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Types of Testing

A protection system consists of circuit breaker(s), instrument transformers, protective relay(s), and a DC system. Every component of this system must perform properly for the system to work reliably.

At Addelec, we pride ourselves on offering the full range of services to ensure your whole system is functioning, not just the individual components.

Standby batteries must provide the equipment they serve with standby power in the event of a power failure. However, the capacity of such batteries can drop significantly for a number of reasons before their calculated life expectancy is reached. This is why it is important to check batteries at regular intervals. The only reliable way of measuring battery capacity is to conduct a discharge test together with battery impedance testing.

Addelec Power Services use the Programma Torkel and Megger Bite 3.

The most carefully set protection is pointless unless the circuit breaker operating times are established. Even the most carefully planned discrimination can fail due to the poor operation of circuit breakers. Our experience shows that many older circuit breakers far exceed their stated opening times. To confirm the opening and closing times of electrically operated circuit breakers Addelec Power Services use the Digi TMR S2 Circuit Breaker Analyser.

The Digi TMR S2 can be operated stand-alone or can be computer controlled. It can fully analyse a circuit breaker’s performance by testing contact time, stroke, velocity and over travel. It measures elapsed time from the instant a breaker coil is powered to the instant of opening or closing of the circuit-breaker’s dry contacts. A built-in hall-effect current sensor records the circuit breaker’s operating coil current amplitude and duration (effectively, a performance “finger print” or current profile). A voltage monitoring input is dedicated to monitoring the substation DC supply or coil voltage (giving a good indication of the station battery system under load).

The Digi-TMR S2 not only times the breaker’s contact response time, but it can also time relays or other switching functions that use an initiating-trigger voltage.

The measurement of the main contact resistance of circuit breakers gives reliable information on the condition of devices particularly after clearing a major fault .The measurement of contact resistance at commissioning stage for fingerprinting purposes gives valuable information for monitoring the device during service. To carry out these measurements we use highly accurate micro-ohm meters.

Prevention is always better than cure – and generally more cost effective!

The reliability of the electric power system depends, in part, on the proper operation of the protective relay systems. The proper operation of any relaying scheme, in turn, relies on the proper voltage and current signals applied to it.

Addelec Power Services uses the CPC100 for CT Testing which is designed to meet the highest standards for performing excitation, ratio, polarity and winding resistance tests on current transformers (CTs) as well as burden-impedance measurement.

The CPC 100 can generate up to 2000 Amps AC with CP CB2 current booster for injecting into the CT‘s primary side and testing its ratio, polarity and burden. For excitation curve measurement, the CPC 100‘s output is connected to the secondary terminals of the core. Our Technician’s can use the CPC 100 to measure the excitation curve and report on the knee point voltage and knee point current (according to the relevant IEC or IEEE / ANSI standard). The CPC 100 also automatically demagnetises the CT core after the test. Using the winding resistance measurement function also allows our Technicians to calculate the accuracy limiting factor (ALF) for protection circuits and the instrument security factor (FS.)

Routine Testing is required to verify correct operation.

CURRENT TRANSFORMER TESTING
  • CT ratio (with burden) up to 800 A or 2000 A with CP CB2, 5 kVA output power
  • CT burden up to 6 A AC | secondary
  • CT excitation curve (knee point) up to 2 kV AC
  • CT Polarity check with CPOL up to 800 A or up to 2000 A with CP CB2, 5 kVA output power
  • Accuracy limiting factor (ALF) test
  • CT ratio with voltage up to 130 V AC | bushing CTs
  • CT winding resistance up to 6 A DC
  • CT voltage withstand test up to 2 kV AC
  • CT ratio Rogowski and CT ratio low power up to 800 A or up to 2000 A with CP CB2, 5 kVA output power
  • Testing is required to identify equipment failures and degradation in service, so that corrective action can be taken.

130kV Power Frequency Test Set is a high voltage AC test system designed to test insulation levels at nominal frequency. It is suited to both commissioning tests and routine maintenance.

Addelec Technicians perform standard stress tests on insulation to between 2 and 3 times the rated voltage to ensure the insulation integrity for normal operation.

In our experience, many power quality issues arise from faulty connections, terminations or faulty switching device, which can lead to variations in voltage and a rise in harmonics. Addelec Power Service’s infrared camera is an effective way of locating poor connections which result in generating heat, even in small amounts. Addelec Power Services can confirm a poor connection by utilising our highly accurate Micro-ohm meters, and repair or replace faulty components.

Addelec Power Services can visit your facility to carry out an on-site assessment of insulating oil quality. The test results are an important deciding factor in ascertaining whether to retain or replace the oil in switchgear, transformers, oil filled cables and other electrical equipment.

OIL DIELECTRIC STRENGTH TESTING

The test kit used by Addelec Power Services (Megger OTS 60PB) is pre-programmed to carry out tests to Australian AS 1767 and International IEC 156 specifications. Addelec Power Services are able to carry out an on-site assessment of insulating oil quality. The test results are an important deciding factor in ascertaining whether to retain or replace the oil in switchgear, transformers, oil filled cables and other electrical equipment.

OIL FILTRATION

Addelec Power Services owns a portable ESI Cold Filter Oil Filtration Unit allowing the following operations to be performed on-site:

  • Transfer of oil into transformers, cable boxes and tap changers
  • Minor oil treatment by use of canister type media filters to remove contaminates and moisture
  • Addelec Power Services also take oil samples to be sent to a NATA laboratory for comprehensive testing of oil
TRANSIENT EARTH VOLTAGES (TEV)

Measuring TEV emissions is a highly effective way of detecting, quantifying and locating PD activity in live assets. The importance of TEV effects (discharges of radio energy associated with PD activity) was first identified by EA Technology in the 1970s to measure ultrasonic emissions.

ULTRASONICS

PD activity creates emissions in both the audible and ultrasonic ranges. The latter is by far the most valuable for early detection and measurement. The Ultra TEV and the Ultra TEV Plus employ ultrasonic sensors, in addition to TEV sensors.

Most importantly, the trigger points on instruments are precisely set to indicate critical PD activity, which is immediately alerted to the Technician, prompting further analysis.

Scheduled tests are essential in detecting effects that can occur within the life cycle of a transformer such as shorted coils, loss of class accuracy due to material changes, or changes to the load.

Turns Ratio Test is used to make sure that the Turns Ratio between the windings of the transformer is correct. This ratio decides what the output voltage of the transformer will be with respect to the input voltage. The ratio is calculated under no-load conditions, with ratios calculated at the tap positions for each winding and for the winding as a whole.

Insulation Resistance Test – The Winding Insulation Resistance test, also known as the Megger test is a measure of quality of insulation within the transformer. It can vary due to moisture content, cleanliness and the temperature of the insulation parts. All measurements are corrected to 20°C for comparison purposes.

The simplest of all, performing routine visual tests can reveal potential problems.

For FRA the company uses an Omicron FRAnalyzer, the FRAnalyzer is a sweep frequency response analyzer for power transformer core and winding diagnosis. Its concept – universal hardware controlled by software running on a computer –A sinusoidal voltage with constant amplitude and variable discrete frequencies is applied to the winding under test and the frequency of the input signal is successively increased.

The FRAnalyzer measures the frequency response of the transformer windings in a wide frequency range and compares it with that in a healthy condition. From the frequency response deviations, many different types of defects in the transformer winding and magnetic core can be diagnosed. These include:

  • Faulty core grounds
  • Partial winding collapse
  • Broken or loose clamps
  • Shorted turns and open windings
  • Core deformation

Protection Relay testing is the primary method of detecting failures, the only other method is to observe a miss operation, which in many cases is too late.

With the Omicron CMC356 or RES APTS – Automatic Protection Test Set, general-purpose test routines can quickly and easily be create and customised to perform automatic relay test programs for virtually any type of protective relay, from any manufacturer. It allows for testing simple or complex, single- or three-phase, electromechanical, solid-state and micro processor based relays. It is not necessary to change the way relays are tested. Addelec Power Services test technicians can substitute for manual test procedures or can easily create new test procedures where previously none existed. This holds for even the most complex relays. After a test program has been created for a specific relay type, it can be stored for recall and repetitive use. It is possible automatically to change voltage, current, phase angle and frequency.

The goal for protection relay testing is to maximise the availability of protection and minimise failure.

The goal with VLF Testing is to stress test the cable, checking for failed or defects in the insulation by growing active partial discharge sites on the insulation.

VT TESTING WITH THE CPC 100

With a voltage output of up to 2000 V AC the CPC 100 can be used to test VT ratio, polarity and burden. By injecting voltage into the primary side, ratio can be measured. Thereby the phase angles of high-voltage output and voltage measurement input are also measured. Thus, the correct VT polarity can be verified. Applying voltage to the secondary VT circuits and measuring the load current in amplitude and phase allows the actual burden to be measured, ensuring that it is within the VT´s specification data.

VOLTAGE TRANSFORMER TESTING
  • VT ratio up to 2 kV AC | polarity and burden
  • VT burden up to 130 V AC | secondary
  • VT secondary voltage withstand test up to 2 kV AC
  • Polarity check with CPOL up to 2 kV AC
  • VT electronics up to 2 kV AC
  • IEC 61850 Sampled Values testing
  • Optimising maintenance schedules increases reliability

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