Electrical and electronics engineering | Types and Facts

Steps to be followed to enhance the life of lithium-ion Batteries

2023-01-08T00:44:00.001-08:00

Use the battery within its recommended temperature range: Lithium-ion batteries perform best when used within a certain temperature range. Avoid exposing the battery to extreme temperatures, as this can reduce its lifespan.
Use the correct charger: It is important to use a charger that is compatible with your lithium-ion battery, as using an incompatible charger can reduce the battery's lifespan.
Avoid overcharging: Lithium-ion batteries should be charged according to the manufacturer's recommendations to avoid overcharging, which can reduce the battery's lifespan.
Avoid fully discharging the battery: It is generally best to avoid fully discharging a lithium-ion battery, as this can reduce its capacity over time. Instead, try to keep the battery level at around 50% when it is not in use.
Avoid using the battery in high drain applications: Using the battery in high drain applications, such as running demanding applications on your smartphone, can drain the battery more quickly and reduce its lifespan.
Store the battery properly: Lithium-ion batteries should be stored in a cool, dry place, and should not be left in a fully discharged state for an extended period of time.

By following these steps, you can help to extend the lifespan of your lithium-ion battery and get the most out of it.

Sources of Lithium

2023-01-08T00:39:00.001-08:00

Lithium is a metallic element that is commonly used in the production of batteries, ceramics, and glass. Lithium ore, or lithium minerals, are a group of minerals that contain lithium as a key component. Some common sources of lithium ore include:

Spodumene: This is a common source of lithium ore, and is a lithium aluminum silicate mineral. It is typically found in pegmatites, which are large, coarse-grained granite bodies that contain rare minerals.
Lepidolite: This is another source of lithium ore, and is a lithium mica mineral. It is typically found in granite and pegmatites.
Amblygonite: This is a lithium-phosphate mineral that is sometimes used as a source of lithium ore. It is typically found in granitic rocks and pegmatites.
Petalite: This is a lithium aluminum silicate mineral that is sometimes used as a source of lithium ore. It is typically found in granitic rocks and pegmatites.
Other sources: Other sources of lithium ore include brines, such as those found in Chile and Argentina, and clay deposits.

Lithium ore is typically mined from open-pit or underground mines, and then processed to extract the lithium. The extracted lithium is then used to produce a variety of products, including batteries, ceramics, and glass.

Safety aspect on using lithium-ion Battery

2023-01-08T00:37:00.000-08:00

Lithium-ion battery packs are widely used in a variety of electronic devices, such as laptops, smartphones, and power tools. These battery packs are known for their high energy density and long lifespan, but there are also some safety concerns to be aware of. Here are some key safety aspects to consider when using lithium-ion battery packs:

Charge and store the battery pack properly: It is important to charge and store lithium-ion battery packs according to the manufacturer's recommendations to avoid overcharging or overheating. Overcharging or overheating can lead to a risk of fire or explosion.
Use a compatible charger: It is important to use a charger that is compatible with the battery pack, as using an incompatible charger can increase the risk of overheating or fire.
Inspect the battery pack regularly: It is a good idea to regularly inspect the battery pack for any signs of damage, such as bulging, swelling, or leaks. If the battery pack shows any of these signs, it should be removed from service immediately and disposed of properly.
Avoid puncturing or crushing the battery pack: Lithium-ion battery packs should be handled carefully to avoid puncturing or crushing them, as this can increase the risk of a fire or explosion.
Dispose of the battery pack properly: When disposing of a lithium-ion battery pack, it is important to follow local regulations and dispose of the battery pack at an approved facility, such as a recycling center or hazardous waste disposal facility. This will help to ensure that the battery pack is disposed of safely and in an environmentally responsible manner.

Lithium-ion Battery

2023-01-08T00:33:00.006-08:00

A lithium-ion battery is a type of rechargeable battery that is widely used in a variety of electronic devices, such as laptops, smartphones, and power tools. These batteries are popular due to their high energy density, which means that they can store a lot of energy in a small space. They also have a relatively low self-discharge rate, meaning that they can hold a charge for a long time without losing their capacity.

Lithium-ion batteries consist of two electrodes, a cathode and an anode, which are separated by a separator. The cathode is typically made of lithium cobalt oxide, while the anode is made of carbon. When the battery is charged, lithium ions move from the cathode to the anode, and when the battery is discharged, the ions move back to the cathode. This movement of ions creates an electric current, which is used to power electronic devices.

Lithium-ion batteries have several advantages over other types of batteries, including a higher energy density, a longer lifespan, and a lower self-discharge rate. They are also relatively lightweight and can be charged and discharged many times before they need to be replaced. However, they can be more expensive than other types of batteries and may pose a risk of fire if they are damaged or improperly used.

SCADA

2023-01-08T00:29:00.005-08:00

SCADA (supervisory control and data acquisition) is a type of control system used in electrical engineering to monitor and control industrial processes and systems remotely. SCADA systems are used in a variety of industries, including power generation and distribution, water treatment, and manufacturing.

SCADA systems typically consist of a central computer or server, which is used to collect data from remote devices and control equipment. These remote devices may include sensors, actuators, and other types of control equipment. The data collected by the SCADA system is used to monitor the status of the system and to make adjustments as needed.

One of the main advantages of SCADA systems is their ability to remotely monitor and control industrial processes and systems. This can reduce the need for on-site personnel, and make it possible to monitor and control processes from a central location. SCADA systems can also improve efficiency by automating certain tasks and allowing for real-time monitoring and control of processes.

There are several components that are typically found in a SCADA system:

Remote terminal units (RTUs): RTUs are devices that are located at remote sites, such as power plants or water treatment facilities. They are responsible for collecting data from sensors and control equipment, and for transmitting this data back to the central computer.
Communication networks: SCADA systems use a variety of communication networks to transmit data between the central computer and the remote devices. This may include wired or wireless networks, or a combination of both.
Human-machine interface (HMI): The HMI is the interface that operators use to interact with the SCADA system. It typically consists of a computer screen and input devices, such as a keyboard or mouse, which allow operators to monitor the system and make adjustments as needed.
Programmable logic controller (PLC): A PLC is a type of computer that is used to control industrial processes and systems. It is typically used in conjunction with a SCADA system to provide automated control of processes.

Overall, SCADA systems are an important tool in electrical engineering, and are used to monitor and control a wide range of industrial processes and systems.

ELECTRICAL SAFETY IN HT INSTALLATIONS

2023-01-08T00:27:00.001-08:00

High tension (HT) electrical systems refer to electrical systems that operate at high voltages, typically above 1000 volts. HT electrical systems are used in various applications, including the transmission of electricity over long distances and the distribution of electricity to large industrial and commercial customers.

Electrical safety is a critical concern when working with HT electrical systems, as the high voltages involved can pose a serious risk of electric shock and other injuries. Some safety measures that electrical engineers should take when working with HT electrical systems include:

Wear personal protective equipment (PPE): When working with HT electrical systems, it is essential to wear the appropriate PPE, including gloves, insulating mats, and face shields. This will help to protect against electric shock and other injuries.
Follow proper procedures: Electrical engineers should follow established procedures when working with HT electrical systems, including proper isolation and grounding procedures to ensure that the electrical system is safe to work on.
Use proper tools: It is important to use the correct tools when working with HT electrical systems, as using the wrong tools can increase the risk of injury. For example, when working on live electrical circuits, it is essential to use insulated tools to reduce the risk of electric shock.
Stay alert: Electrical engineers should stay alert and be mindful of their surroundings when working with HT electrical systems. This includes being aware of the location of other workers and equipment, and avoiding distractions that could increase the risk of injury.

By following proper safety measures, electrical engineers can minimize the risk of injury when working with HT electrical systems.

GUIDE TO ENERGY AUDIT ON ELECTRICAL

2023-01-08T00:11:00.003-08:00

An energy audit is a process for evaluating the energy efficiency of a building or system. Electrical engineers can play a key role in conducting energy audits, as they have expertise in analyzing electrical systems and identifying areas for improvement. Here are some steps that an electrical engineer might follow when conducting an energy audit:

Gather data: The first step in an energy audit is to gather data on the building or system being evaluated. This may include information on the size and age of the building, the types of electrical equipment and systems being used, and the energy consumption of these systems. This data can be collected through a variety of methods, such as reviewing utility bills, conducting interviews with building occupants and staff, and using measurement devices to gather data on energy usage.
Identify areas for improvement: After collecting data, the electrical engineer will analyze the information to identify areas where energy efficiency can be improved. This may involve looking for equipment or systems that are using more energy than necessary or identifying opportunities to upgrade equipment to more energy-efficient models.
Develop recommendations: Based on the findings of the energy audit, the electrical engineer will develop recommendations for improving energy efficiency. These recommendations may include measures such as upgrading lighting systems, improving insulation, or installing energy-efficient appliances.
Implement recommendations: Once the recommendations have been developed, the electrical engineer can help to implement them by working with contractors and building staff to make the necessary changes. This may involve designing and installing new electrical systems or modifying existing systems to be more energy efficient.
Monitor progress: After the recommendations have been implemented, the electrical engineer can help to monitor the progress of the energy efficiency measures and make any necessary adjustments. This may involve collecting data on energy usage before and after the changes were made to determine the impact of the improvements.

7. Electrical Question & Answer (Points) for Tests / Interview

2017-09-06T07:16:00.002-07:00

Ø AC bridge circuits such as wheatstone, Maxwell’s Inductance Bridge etc., are used for the precision measurement of AC resistance, capacitance and inductance.

Ø Active power is obtained by multiplying kVA by cos φ and its unit is kW

Ø As per Kirchhoff’s current law, in any electrical network, the phasor sum of the currents meeting at a junction is zero.

Ø As per Kirchhoff’s voltage law, the phasor sum of the voltage drops across each of the conductors in any closed path (or mesh) in a network plus the phasor sum of the e.m.fs. connected in that path is zero.

Ø Maxwell’s L/C bridge is so called because for balance, it uses two opposite impedances in opposite arms.

Ø Maxwell-Wien bridge is used for measuring inductance.

Ø Power Factor may be defined as the ratio of true power / apparent power i.e (W/VA)

Ø Reactive power is known as reactive kVA and is obtained by multiplying kVA by sin φ. It is written by kVAR.

Ø The P.F of an R-C circuit is between zero and 1.

Ø The unit of admittance is Siemens.

Ø The unit of capacitive susceptance is Siemens.

6. Electrical Question & Answer (Points) for Tests / Interview

2017-09-06T07:15:00.000-07:00

Ø The reduction of battery capacity at high rates of discharge is primarily due to the rapid formation of lead sulphate on the cell plates.

Ø The time taken by an alternating quantity to complete one cycle is called its time period (T). (e.g. 50-Hz alternating current has a time period of 1/50 second)

Ø The number of cycles/second is known as the frequency of the alternating quantity. Its unit is hertz (Hz).

Ø The maximum value, positive or negative, of an alternating quantity is known as its amplitude.

Ø The r.m.s. value of an AC is given by that steady (DC) current which when flowing through a given circuit for a given time produces the same heat as produced by the AC when flowing through the same circuit for the same time.

Ø For the symmetrical sinusoidal current, r.m.s. value is 0.707 × maximum value of current.

Ø The r.m.s. value of a complex current wave is equal to the square root of the sum of the squares of the r.m.s. values of its individual components.

Ø Average value of current is 0.637 × maximum value of current.

Ø R.M.S. value is always greater than average value except in the case of a rectangular wave when both are equal.

Ø Form factor is defined as the ratio of r.m.s value / average value (i.e. 1.11)

Ø Vectors are a shorthand for the representation of alternating voltages and currents and their use greatly simplifies the problems in AC work.

Ø Various forms or methods of representing vector quantities are Symbolic Notation, Trigonometrical Form, Exponential Form and Polar Form.

Ø Power Factor may be defined as the cosine of the angle of lead or lag.

Ø Power Factor may be defined as the ratio of resistance / impedance (R/Z).

5. Electrical Question & Answer (Points) for Tests / Interview

2017-09-06T07:13:00.000-07:00

Ø A moving coil voltmeters measures only DC voltages.

Ø Bench charge is given to the battery when taken off the vehicle.

Ø Damping force acts on the moving system of an indicating instrument only when it is moving.

Ø During the charging and discharging of a nickel iron cell water is neither formed nor absorbed.

Ø Eddy current is the most efficient form of damping employed in electrical instruments.

Ø Floating battery systems are widely used for power stations, emergency lighting and telephone exchange installations.

Ø kWh meter can be classified as recording instrument.

Ø Moving iron instruments can be used for measuring direct currents and voltages and alternating current and voltages.

Ø One complete set of positive and negative values of alternating quantity is known as one cycle.

Ø Permanent magnet moving coil ammeter have uniform scales because they are spring-controlled and their deflecting torque varies directly as current.

Ø Permanent magnet type meter is suitable for only direct current measurements.

Ø Sediment accumulates at the bottom of a lead-acid battery consists largely of antimony-lead alloy.

Ø The efficiency of a nickel-iron cell is less due to its higher internal resistance.

Ø The hot-wire ammeter reads equally well on DC and / or AC circuits.

Ø The moving system of an indicating type of electrical instrument is depending upon a deflecting torque, controlling torque and damping torque.

Ø The reduction of battery capacity at high rates of discharge is primarily due to the rapid formation of lead sulphate on the cell plates.

4. Electrical Question & Answer (Points) for Tests / Interview

2017-09-06T07:10:00.000-07:00

Ø The magnetising force at the centre of a circular coil varies directly as the current, varies directly as its radius and varies inversely as its radius.

Ø The ratio of Ah efficiency to Wh efficiency of a lead-acid cell is always greater than one.

Ø The resistance offered to the radial leakage (at right angles to the flow of useful current) of current is called insulation resistance of the cable.

Ø The SI unit of electric intensity is V/m (volt/metre) or N/C (newton/coulomb).

Ø The SI unit of magnetic flux is weber.

Ø The unit of absolute permittivity of a medium is farad/metre.

Ø The unit of capacitance is coulomb/volt i.e. farad

Ø The various electrical instruments can be divided into absolute instruments and secondary instruments.

Ø The working principle of thermo-couple ammeter is based on the Seebeck effect.

Ø Trickle charging of battery is used to balance the open-circuit losses.

Ø Two heaters, rated at 1000 W, 250 volts each, are connected in series across a 250 Volts 50 Hz A.C. mains. The total power drawn from the supply would be 500 watt.

Ø Two similar electric charges of 1 C each are placed 1 m apart in air. Force of repulsion between them would be nearly 9 × 109 newton.

Ø Two types of e.m.f are dynamically induced and statically induced.

Ø Trickle charging of a storage battery helps to keep it fresh and fully charged.

Ø Sulphation in a lead-acid battery occurs due to incomplete charging.

Ø The constant-voltage system of charging a lead-acid cell has the advantage of reduced time of charging and increased cell capacity.

Ø The capacity of a lead-acid cell does not depend on its rate of charge.

3. Electrical Question & Answer (Points) for Tests / Interview

2017-09-06T07:07:00.000-07:00

Ø Maxwell’s loop current method of solving electrical networks utilizes Kirchhoff’s voltage law.

Ø Megger is a portable instrument used for testing the insulation resistance of a circuit in terms of Mega ohms.

Ø One farad is the capacitance of a capacitor which requires a charge of one coulomb to establish a potential difference of one volt between its plates.

Ø One kWh of energy equals nearly 860 kcal.

Ø Permanent magnets are normally made up of alnico alloys.

Ø Relative permeability of vacuum is 1.

Ø Secondary instruments are those, in which the value of electrical quantity to be measured can be determined from the deflection of the instruments, only when they have been pre-calibrated by comparison with an absolute instrument.

Ø Sources for Generation of Electricity using Conventional methods are Thermal and Hydro-Electric.

Ø Sources for Generation of Electricity using Non-Conventional methods are wind power, photo-voltaic cells and Fuel cells.

Ø Statically induced e.m.f is further sub-divided into mutually induced e.m.f. and self-induced e.m.f.

Ø The algebraic sign of an IR drop is primarily dependent upon the direction of current flow.

Ø The capacitance of a capacitor is not influenced by plate thickness.

Ø The capacity of a cell is measured in ampere-hours.

Ø The damping force in an instruments can be produced by air frictions, eddy currents and fluid friction.

Ø The direction of the induced current is decided by applying either Fleming’s Right-hand Rule / Flat-hand rule / Lenz’s Law.

Ø The electric energy required to raise the temperature of a given amount of water is 1000 kWh. If heat losses are 25%, the total heating energy required is 1333 kWh.

2. Electrical Question & Answer (Points) for Tests / Interview

2017-09-06T07:05:00.003-07:00

Ø During the charging of a lead-acid cell its voltage increases.

Ø Electric flux emanating from an electric charge of + Q coulomb is Q.

Ø Electromagnetic effect is utilized for wattmeters and watthour meters.

Ø Electrostatic effect is utilized only for voltmeters only.

Ø End-cell control system is an economical system developed and used in place of using rheostat in batteries for controlling the voltage.

Ø For a given line voltage, four heating coils will produce maximum heat when all the four coils connected in parallel.

Ø For any medium, electric flux density D is related to electric intensity E by the equation D = ε ₀ ε _rE

Ø If a 220 V heater is used on 110 V supply, heat produced by it will be one-fourth as much.

Ø If D is the electric flux density, then value of electric intensity in air

is D = ε_o

Ø If dielectric slab of thickness 5 mm and ε_r = 6 is inserted between the plates of an air capacitor with plate separation of 8 mm, its capacitance is almost doubled.

Ø If relative permittivity of mica is 5, its absolute permittivity is 5 ε_o.

Ø In practice, earth is chosen as a place of zero electric potential because it has almost constant potential.

Ø Induction type instruments are used for AC measurements only. It can be used either as ammeter, voltmeter and wattmeter.

Ø Inside a charged conducting sphere, the potential and electric intensity is Zero.

Ø Inside a conducting sphere, potential remains constant.

Ø Kirchhoff’s current law is applicable to junctions in a network.

Ø Kirchhoff’s voltage law is concerned with IR drops and battery e.m.f.

Ø Magnetic effect, Thermal effect, Electrodynamic effect and Electromagnetic effect is utilized for ammeters and voltmeters.

1. Electrical Question & Answer (Points) for Tests / Interview

2017-09-06T07:02:00.002-07:00

Ø A capacitor consists of two conductors separated by an insulator.

Ø A force of 10,000 N accelerates a body to a velocity 0.1 km/s. Then, the power developed is 1000 kW.

Ø Absolute instruments are those which give the value of the quantity to be measured, in terms of the constants of the instrument and their deflection only.

Ø According to Faraday’s Laws of Electromagnetic Induction, an e.m.f. is induced in a conductor whenever it cuts magnetic flux.

Ø According to Gauss’s theorem, the surface integral of the normal component of electric flux density D over a closed surface containing charge Q is Q.

Ø A 100 W light bulb burns on an average of 10 hours a day for two weeks. The weekly consumption of energy will be 14 units.

Ø According to Kirchhoff’s voltage law, the algebraic sum of all IR drops and e.m.f. in any closed loop of a network is always zero.

Ø Active materials of a lead-acid cell are lead peroxide, dilute sulphuric acid and sponge lead.

Ø Advantages of Nuclear Generation is that the Quantity of fuel required is small for generating a given amount of electrical energy, compared to other fuels. It is more reliable, cheaper for running cost, and it is efficient.

Ø An e.m.f and the current is induced in any conductor which is cut across or is cut by a magnetic flux is known as electromagnetic induction.

Ø Chemical effect is utilized for DC ampere-hour meters.

Ø Circle diagrams are useful for analysing the operating characteristics of circuits, which, under some conditions, are used in representing transmission lines and AC Electrical machineries.

Ø Damping force is one which acts on the moving system of the instrument only when it is moving and always opposes its motion.

Ø Disadvantages of Nuclear Generation is that the Fuel is expensive and not abundantly available everywhere. It has high capital cost and maintenance cost. Disposal of Nuclear waste is a problem.

Current Transformer Burden Ammeter

2016-11-01T05:44:00.000-07:00

Current Transformer Burden Ammeter is a rugged, portable instrument, designed to field-test current transformer installations for:

_ short-circuited secondary turns

_ short-circuited primary turns

_ short-circuited secondary wiring

_ high-resistance connections in the secondary circuit

_ grounding of secondary winding when mounted on a grounded structure

_ grounding of a normally ungrounded wire

APPLICATIONS

Within the accuracy limits of the CT, a good current transformer should not have a noticeable change in ratio when a secondary burden is added. This is because the primary effect of additional burden on a good CT is a rise in the secondary voltage.

However, if one or more turns of a CT are shorted, a substantial amount of the total available ampere-turns is diverted into the shunt path created by the short. Thus, the current to the circuit connected to the CT is less than

the CT’s total secondary current.

Therefore, when the proper burden within the ammeter is added in series with the circuit connected to a good CT, the current indicated by the ammeter should only decrease a few percent.

However, in a bad CT, the additional burden will cause even more current to be diverted into the shorted turn(s). This will cause the current indicated on the ammeter to decrease significantly. This sudden and large decrease in the ammeter reading will be seen immediately whenever the burden is added by using the switch.

FEATURES AND BENEFITS

_ Multi range ammeter incorporating switch-selected burdens

_ The burdens are normally shorted out, but can be put in series with the ammeter by a spring-loaded momentary switch

_ Designed to ensure that the secondary of the CT under test will not be accidentally opened; make-before-break construction used for ammeter range and burden selector switches

_ The instrument is housed in a rugged, moulded-plastic case. All leads extend away from the user to prevent contact with live components.

Arc Reflection Filters

2016-11-01T05:42:00.001-07:00

Arc Reflection Filters marry impulse generators to high voltage “radars” (time domain reflectometers, TDR), providing fault locating crews with integrated systems to meet all cable fault locating needs. Two models are available:

_ Standard Arc Reflection Filter (detachable):

designed to withstand 1,000,000 Joules/hour (continuous operation with a standard impulse generator) and 50 kV proof/burn voltage.

_ Heavy-Duty Arc Reflection Filter (detachable):

designed to withstand over 3,000,000 Joules/hour (continuous operation with a heavy-duty impulse generator) and 70 kV proof/burn voltage. Choice of an Arc Reflection Filter is dependent upon the energy producible by the impulse generator with which it will be used. The Standard Arc Reflection Filter can be used with any non-heavy-duty impulse generator. The Heavy-Duty Arc Reflection Filter is used whenever the system includes a heavy-duty style impulse generator (generates in excess of 1,000,000 Joules/hour and/or 70-kV proof/burn voltage). The arc reflection filter, including its sturdy metal cabinet of welded construction and all its components are designed to withstand the rough handling it will experience in the field. For operator convenience, a mode selector switch is provided on the top control panel. When the selector switch is set to ARC REFLECTION TEST, the arc reflection filter network is connected to the cable under test. This makes it possible for the operator to make either TDR tests or arc reflection tests, as well as other tests requiring the use of the filter. When the selector switch is set to the PROOF/BURN/ IMPULSE mode, the filter is bypassed, allowing stand-alone operation of the impulse generator system on impulse, proof or burn. A wide-band current transformer is permanently connected electrically and mounted inside the cabinet for use with the surge pulse.

APPLICATIONS

With Arc Reflection Filters, cable faults can be located on power cables rated at up to 35 kV. Relatively small systems, such as most direct buried underground residential distribution (URD) systems, are easily satisfied with the standard filter. Larger systems, including especially long direct buried distribution cable and especially complex circuits using lead-covered cable, require much more energy (such as is made possible using the heavy-duty filter).

FEATURES AND BENEFITS

Designed to withstand continuous operation

_System is not vulnerable to operator error (if left on after fault localization).

_System can be operated for the time required to localize complex faults.

_Operator can use the full proof-burn capability of the thumper in use.

Components designed as distributed circuit elements

_ Helps to provide a clear, distinct display on the companion TDR.

_ Helps to eliminate unwanted background reflections on the companion TDR by contributing less than 5% noise.

Slow voltage rise time

_ Limits the voltage that reaches the cable under test to the voltage required to break down the fault.

_ Operator cannot overstress a faulted cable while in the arc reflection mode.

Low output impedance

_ More effective in energizing large cable/network systems.

_ Improved fault locating capability.

High output current capability

_ Ionizes faults immersed in oil or water

_ Power matches the fault for more effective fault locating

Cable Route Tracer

2016-11-01T05:41:00.002-07:00

The AccuTrace Cable Route Tracer consists of a transmitter, which energizes the line with a traceable signal, and a portable receiver, which detects the signal. The transmitter can energize the line either by magnetic induction from a built-in antenna or by direct conductive connection to the Metallic line. Energizing the line conductively provides increased tracing distance and minimizes signal coupling to other lines. Inductive coupling, which does not require a mechanical connection to the line, permits a buried line to be traced without uncovering or de-energizing it. The transmitter provides a simple, LO/HI pushbutton to adjust the transmitted signal’s strength, and a PULSE button for battery conservation and easy identification of the signal. The receiver can be used to trace lines using either peaks (detection of the maximum signal) or nulls (detection of the minimum, or zero, signal). The antenna is swivel-mounted for operation in vertical, horizontal or 45° mode used to calculate depth. The receiver provides audible and visual indication of detected signal strength. Simple controls adjust sensitivity and amplification, and a jack provides for audio output to an optional headset. Standard AA batteries provide up to 30 hours of continuous operation. When the receiver is not in use, the telescoping handle retracts for convenient, compact storage.

APPLICATIONS

AccuTrace locates and traces any conductive line such as cable, pipe or metallic conduit. Depth of the line can be established quickly by taking advantage of the swivel mounted antenna. Adding an optional ring clamp to the system provides a stronger inductive signal for tracing in areas with heavy cable activity. Blockages in water pipes such as sewer lines can be found with the use of an optional watertight capsule transmitter. A tape-on

Transmitter lets the operator locate collapsed duct work.

FEATURES AND BENEFITS

_ Easy to use and simple to operate, this cable route tracer can be used successfully the first day in the field.

_ Conductive coupling lets the operator discriminate between multiple utility cables in a common trench and trace the line of interest. Conductive tracing also increases tracing distance.

_ Inductive coupling lets the signal be transmitted without a direct metal-to-metal connection. The operator can trace an energized cable using a distinctive transmitted signal. Also, cables that do not have exposed terminations can be traced with ease.

_ Both peak- and null-tracing mode methods can be used during a single trace to ensure accuracy and speed. Null tracing is very fast and can be used to identify sharp direction changes. Peak tracing can be used to find the cable at the start of the trace and to identify cable location when conditions make null tracing ineffective. Super inductive circuitry allows, in the inductive tracing mode, the AccuTrace to trace longer lengths than any known competitor. If conditions such as cable depth make normal inductive tracing inefficient, the superinductor will produce a signal that the receiver can trace.

_ The receiver picks up only the distinctive transmitted signal by filtering out electric noise and static.

_ Extremely loud, adjustable audio output eliminates the need for headphones in noisy areas. This makes the AccuTrace more comfortable and easier to use than units requiring headphones and visual interpretation.

_ Extremely lightweight receiver increases operator comfort when tracing long cables or when using for extended periods.

Cable Phasing Meter

2016-11-01T05:40:00.001-07:00

Cable Phasing Meter offers a safe and quick method of measuring voltage and determining phase rotation of underground distribution systems using the capacitance test point of elbow connectors. Most manufacturers of high-voltage cable terminators incorporate capacitance test points into their elbow connectors. These test points are designed for measuring purposes.

APPLICATIONS

The Cable Phasing Meter is an instrument designed to measure voltage, determine phase potation and phase out cables when connected to the capacitive test points. This instrument is battery operated and is supplied with a ground and two measuring leads.

FEATURES AND BENEFITS

_ Safe - operates at low voltage

_ Measures system voltage

_ Measures capacitance of test point if system voltage is known

_ Checks phase rotation of cables

_ Phases out cables

_ Rugged; comes with portable case

_ Battery operated

_ Operates from potential test point of elbow connectors

AC Dielectric Test Sets

2016-11-01T05:39:00.001-07:00

The 50/100 kV AC Dielectric Test Sets are ac high-voltage sources for testing electrical insulation. The standard system includes a control/instrument cabinet, a high-voltage transformer assembly and all necessary cables including ground and input power.

The high-voltage transformer is installed in an oil-filled, heavy-duty, fibreglass tank permanently mounted on a cart with casters. Convenient points are provided on the tank top (0 to 100 kV) and side (0 to 50 kV) for connection to the high-voltage output. A voltage divider is permanently connected to the output terminals and installed inside the high-voltage tank for mechanical protection. A wing nut is provided on the cart for the ground connections. Storage space is provided on the cart for the control cabinet, instruction manual and cables.

APPLICATIONS

These test sets consist of general-purpose ac high-voltage sources suitable for dielectric withstand (high-potential) testing of all types of electrical insulation. They also permit guarded leakage current measurements and are suitable for use with capacitance and dissipation factor bridge systems to measure insulation power factor.

The Megger 681100 Series test sets are recommended for testing capacitive loads that fall under the capability curve. Most electrical insulation systems are principally capacitive. Operation from 50-Hertz input supply permits a 20% increase in maximum load capability.

The Megger 686100 Series test sets are recommended for special applications involving resistive loads, or small capacitive loads with extended test durations.

FEATURES AND BENEFITS

_ Suitable for testing aerial bucket trucks according to ANSI A92.2

_ 50-kV tap with doubled output current permits testing bucket liners according to ANSI A92.2

_ Built-in, four-range output current meter with guard circuit

_ Four-range output kilovoltmeter has accuracy unaffected by sample loading

_ High-speed overvoltage and over current trip-out holds test voltage reading at instant of trip-out

_ Output signals are provided for both voltage and current meters, on all ranges, to permit external recording of test data

_ Zero-start safety interlock system with provision for external safety interlocks and warning lights

_ 15-ft (4.6-m) inter-unit cables, separate control and high voltage units for safety during tests

DC Dielectric Test Sets

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Dielectric test sets measure leakage current while applying a dc voltage at or above the insulation system’s operating level. This measurement aids in determining the insulation system’s ability to withstand over voltages such as lightning strikes and switching surges.

APPLICATIONS

Portable DC dielectric test sets check the electrical insulation quality of motors, power cables, switchgear, insulators, transformers and capacitors. Typical applications include acceptance and maintenance testing of critical equipment used by electrical utility substations and industrial plant distribution systems. Power apparatus manufacturers may also use the equipment to perform QA/QC production tests. The test sets can be used to perform step-voltage and proof tests which, when incorporated into a routine maintenance program, can aid in predicting potential failure before breakdown occurs.

Two models are available; a 5-kV unit for testing equipment rated 2.5 kV and below, and a 15-kV model for use on equipment rated 7.5 kV and below. Both are suitable for testing power cable, switchgear and rotating machinery in accordance with IEEE, ICEA, NEMA and ANSI guidelines.

Megger DC dielectric test sets act like full-wave rectified units, they also are suitable for applications involving vacuum bottles.

DC vs AC High-Potential Testing

Direct current high-potential testing provides several advantages over alternating current. Direct current test equipment uses far less power, provides fast charging of highly capacitive test samples, can be easily transported to the test site and costs less. Additionally, the dc test can detect incipient breakdown without the possibility of damage to good insulation.

FEATURES AND BENEFITS

_ Compact and portable

_ Air insulated, uses no oil

_ ±2% accuracy

_ Leakage current measurement as low as 0.1 mA

_ Continuously variable test voltage with zero-start safety interlock

_ Fast charging of high-capacitance samples

_ Current guard circuit for highly accurate measurements

_ Strip chart recorder for hard copies (optionally available)

Safety and Reliability

_ Input and output line circuit breaker

_ Output current overload relay

_ Zero-start interlock for high-voltage output

_ Pushbutton controls and indicating lights for high voltage ON/OFF

_ Full circuit breaker protection

_ Connection for external permissive and safety interlocks

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Note: Special precautions and provisions may be necessary for current measurement in CT secondary circuits and such measurement techniques are outside the scope of the guidance in this document.

Where current measurements are to be made using instruments other than insulated tong-test type instruments, the connections should be made with the apparatus dead, and should be made secure before the power is switched on. Any such temporary connections need to be adequately rated both for current and voltage.

If regular testing needs to be done, for example on complex control panels, nearby bare live conductors should not be accessible (eg screened) where access is not required. Alternatively, purpose-made screened test points or instrumentation may be provided.

Examination of equipment

All items of test equipment, including those items issued on a personal basis, should receive a regular inspection and, where necessary, a test by a competent person. Records are recommended to be kept of inspection and testing of the equipment, particularly where faults are found. These records will help decide how often visual inspection or testing will need to be carried out. It is important that electricians are aware of the kinds of defect which may occur in test equipment. Examples of common faults are:

(a) Cracked meter cases;

(b) Damaged insulation (abrasion, cuts or perishing of flexible insulation);

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Precautions during testing

For voltage detection or measurement, test leads protected by a fuse (or fuses) are recommended when voltmeters and in particular multimeters, are used. Although some multimeters are fitted with electromechanical overload devices, these are often inadequately rated to deal with short circuit energy present on electrical power systems. It is usually necessary to use leads which incorporate high breaking capacity (hbc) fuses even if the multimeter has an overload trip. If terminal clips are provided for connection to test points, they should be adequately insulated and arranged to be suitable for use with the test leads, as a safe alternative to the use of test probes. It is important that a multifunction or multirange meter is set to the correct function and/or range before the connections are made. Where there is doubt about the value of voltage to be detected or measured, the highest range should be selected at first, provided that the maximum voltage possible is known to fall within the range of the instrument.

Progressive voltage detection or measurement is often used to prove circuit continuity. The dangers from exposed live conductors should be borne in mind when using this method. In many cases, continuity testing can be carried out safely with the apparatus dead, using a self-contained low voltage dc source and indicator.

If tong-test instruments are to be used, it is necessary to check first that there is adequate working space free from danger (ie from bare live conductors at dangerous voltages) at the place where the instrument will be held. The tong insulation should always be examined visually before the instrument is used; if defects are present the instrument should not be used.

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Precautions before testing

Before testing begins it is essential to establish that the test device including all leads, probes and connectors is suitably rated for the voltages and currents which may be present on the system under test.

Before any testing is carried out ensure that:

(a) The equipment which is to be worked on is safe for the intended tests; and

(b) The working environment does not present additional dangers. These dangers include:

(i) Inadequate space to work safely;

(ii) An insecure footing;

(iii) Insufficient light;

(iv) Potentially flammable gases or vapours;

(v) Explosive or conductive dusts.

Where a test is being made simply to establish the presence or absence of voltage, the preferred method is to use a proprietary test lamp or 2-pole voltage detector suitable for the working voltage of the system rather than a multimeter. Accident history has shown that the use of incorrectly set multimeters or makeshift devices for voltage detection has often caused accidents.

Note: Test lamps and some voltage indicators may fail to danger, eg. a faulty lamp not indicating a live circuit. These devices should be proved before and after use on a known live source of similar voltage to the circuit under test, or alternatively on a portable test source.

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Test lamps and voltage indicators are recommended to be clearly marked with:

(a) The maximum voltage which may be tested by the device; and

(b) Any short time rating for the device if applicable. This rating is the recommended maximum current which should pass through the device for a few seconds. These devices are generally not designed to be connected for more than a few seconds.

The use of test equipment by electricians falls into three main categories:

(i) Testing for voltage (voltage detection);

(ii) Measuring voltages; and

(iii) Measuring current, resistance and (occasionally) inductance and capacitance.

Item (a) forms an essential part of the procedure for proving a system dead before starting work but may also be associated with simple tests to prove the presence of voltage. Items (b) and (c) are more concerned with commissioning procedures and fault finding.

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Sockets and terminals

Risks of inadvertent hand or finger contact with any live test socket conductor when the equipment is live need to be reduced. The terminals and test sockets of test equipment may require shrouding.

Voltage detection instruments

Instruments used solely for detecting voltage fall into two categories. These are:

(i) Detectors which rely on an illuminated bulb (test lamp) or a meter scale (test meter). Test lamps fitted with glass bulbs should not give rise to danger if the bulb is broken. It may be protected by a guard. These detectors require protection against excess current. This may be provided by a suitable high breaking capacity (hbc or hrc) fuse or fuses, with a low current rating (usually not exceeding 500 mA), or by means of a current-limiting resistor and a fuse. These protective devices are housed in the probes themselves. The test lead or leads are held captive and sealed into the body of the voltage detector.

(ii) Detectors which use two or more independent indicating systems (one of which may be audible) and limit energy input to the detector by the circuitry used. An example is a 2-pole voltage detector, i.e. a detector unit with an integral test probe, an interconnecting lead and a second test probe. These detectors are designed and constructed to limit the current and energy which can flow into the detector. The limitation is usually provided by a combination of circuit design, using the concept of protective impedance, and current limiting resistors built into the test probes. These detectors are provided with in-built test features to check the functioning of the detector before and after use. The interconnecting lead and second test probe are not detachable components. These types of detector do not require additional current limiting resistors or hbc fuses to be fitted provided that they are made to an acceptable standard and the contact electrodes are shrouded.