Testing the Safety of High-Voltage Systems
Up to the Mark: HBM Measuring Equipment for High-Voltage Tests
HBM has supplied three transient recorders from the Genesis High Speed range to the KEMA High Voltage Laboratory at DNV GL in Arnhem. The new data acquisition systems replace the LDS Nicolet equipment that KEMA Laboratories acquired between 1995 and 2000 and used until recently. The main reason for changing over to new measuring equipment was the application of the IEC 60060-2 (2010) standard, which provides guidelines for performing high-voltage tests and the requirements concerning measuring technology.
Power failures have significant consequences
In the High Voltage Laboratory we have focused on testing and certificating HV components, power equipment and metering, protection and control equipment for the generation and distribution of electricity. Testing and certifying the safety and control of high-voltage installations and systems is becoming increasingly important, because the electricity infrastructure is getting more and more complex and vulnerable. Power failures have significant consequences, ranging from considerable economic damage to life-threatening situations as a result of the failure of critical systems.
"We have built up a considerable reputation in the field. Our KEMA Type Test certificates are internationally recognised.”
John Mooren, test engineer at KEMA Laboratories in Arnhem.
About KEMA Laboratories
Installations and equipment are tested in the High Voltage Laboratory and the High Power Laboratory in Arnhem, both of which are part of KEMA Laboratories, which in turn comes under the Energy division of DNV GL. The High Power Laboratory performs short circuit tests to determine the short circuit resistance of materials. Four generators were used to create a short circuit current of 8,800 MVA, and this was increased to 13,000 MVA in 2015 by the acquisition of two new generators.
The High Voltage Laboratory is chiefly occupied in testing and certifying high-voltage cables and components as commissioned by manufacturers. This mainly consists of dielectric tests that determine the insulation characteristics of materials. The laboratory also performs a wide range of other tests, such as the temperature testing of transformers and switching installations, endurance tests lasting several months, high voltage calibration and mechanical tests of items including insulators and safety relays.
Dielectric tests are carried out using, among others, alternating current (AC), direct current (DC) and lightning impulse (LI). The HBM transient recorders are used to record tests with lightning impulse. A standard lightning impulse voltage waveform has a front duration of 1.2 microseconds and a time to half value of 50 microseconds. The HBM transient recorder system has a very high measuring speed of 10 nanoseconds. The front duration of a waveform is determined by taking approximately 120 measurements in 1200 nanoseconds. The peak voltage of a lightning waveform is evaluated using software formulae that conform to IEC 60060-2. This software is part of the HBM computer system that processes the measurement data, and the transient recorders from the HBM Genesis High Speed range are extremely suitable for this task.
Lightning surge voltage
The lightning surge voltage is created by an impulse voltage generator, which consists of a number of 100 kV (or 200 kV) capacitors that are charged and then discharged in series. There are a total of three impulse voltage generators in the High Voltage Laboratory. The maximum voltage achievable is 2.6 MV (13 capacitors of 200 kV each), and voltages of 1.6 MV and 1 MV (16 and 10 capacitors of 100 kV each respectively) are also possible. The peak value of the impulse voltage is established in accordance with international standards. The peak value of the impulse voltage for 400 kV high-voltage systems is 1425 kV, and for 12 kV medium-voltage systems it is 75 kV.
The laboratory contains six high-voltage dividers, which are used to measure impulse voltages. Each divider has its own digitizer transmitter, and there are also two measuring systems with which secondary signals can be measured. There are a total of eight transmitters and three receivers, plus three HBM PCs/measuring systems.
Another new feature was the separation of data acquisition and the transfer of the measurement data to a PC via optical fibre. This has many benefits because it eliminates interference, which makes the measurement data more accurate. Safety is also improved, because the flash-over of high voltage via optical fibre is not possible. Exposure to such voltages is fatal.
Why new equipment?
“It was decided in 2009 to replace the existing equipment. This was not just because of the move to the new laboratory in 2009, but was mainly as a result of the changes to the IEC 60060 standard, which came into effect in 2010”. As HVL we have a seat on the IEC standards committee, because you want to keep up to date and to test and certify in accordance with the most modern standards. The IEC 60060 standard describes uniform conditions for high-voltage tests. It specifies precise definitions and guidelines for generating the voltage required for the tests and describes the requirements for performing the tests with the permitted measurement tolerances, as well as the requirements applicable to the measuring systems.''
John Mooren, test engineer at KEMA Laboratories in Arnhem.
A proposed investment for acquiring new measurement equipment was approved in 2010, after which tenders were invited from five leading manufacturers. After selecting from the tenders, three manufacturers were invited to give demonstrations in the laboratory in 2011. The eventual choice on the basis of the best price-to-performance ratio was for HBM.
By choosing HBM, DNV GL effectively stayed with the same equipment, because HBM had taken over the activities of LDS Nicolet and brought the renewed equipment to the market in 2009 under the name of Genesis High Speed. This modular product line is intended for super-fast data acquisition and transient recording. The data acquisition equipment is used in endurance tests, ballistic tests, short circuit and lighting impulse voltage tests, among others.
The new equipment was delivered at the beginning of 2012. This comprised three ISOBE5600m transient recorders from the Genesis Speed range with a sample rate of 100MS/s, which is 100 million samples per second. An ISOBE5600 system consists of a digitizers/transmitter unit that is installed in the high voltage test environment and a receiver unit in another location that can be connected to a data acquisition system or a PC. Communication between transmitter and receiver is via optical fibre, which ensures total electrical insulation between the test cell and the control room. HBM Perception Software for processing the measurement data is also part of the solution and performs the calculations described in IEC 60060-2.
The HBM ISOBE5600t transmitters/digitizers in the HVL have attenuators that process the incoming signals, installed as fixed units in an EMC box, which means that measurement results cannot be affected by electromagnetic interference. The EMC boxes are connected to the dividers. The digitizer/transmitters digitize the measurement signals and makes them suitable for transmitting to the receiver via a fibre optic cable. The Perception High Voltage Impulse Analysis (HV-IA) software module provides a control panel for setting up the tests, as well as a graphic user interface with which most of the functions can be visualized, for example as voltage curves. The ISOBE5600r receiver, together with a control panel and a PC, is installed in a measurement room. The data are presented in LabVIEW via an interface with the Perception Software.
The initial configuration was operational and accredited in 2012, after which it was integrated with LabVIEW. The last Nicolet was withdrawn from use at the end of 2015 and the DNV-GL High Voltage Laboratory switched over completely to using Genesis High Speed equipment. The new equipment has turned out to be noticeably more accurate than the old system, as it has the facility to perform and report on tests in full compliance with the IEC 60060 standard.
*HBM Genesis High Speed products were previously marketed under the LDS Nicolet, LDS Dactron and Gould Nicolet brands. The Nicolet brand is owned by Thermo Fisher Scientific Inc. Corporation. Gould is a brand of Gould Electronics GmbH.