Protection History

Authors: Walter Schossig, Germany, and Thomas Schossig, OMICRON electronics GmbH, Austria

Relay Testing ? Test Sets and testing Technology in the 1980s

Further developments in protection testing resulted in portable devices, especially for distance protection, directional earth fault relays, generator protection and railways auxiliary functionalities. Some of them have been mounted directly in the cubicles. This was also valid for testing devices. Figure 1 shows such an example of Sprecher + Schuh (Austria, 1980). This device allowed simple and fast check of primary relays types MU, MT and MUT at nominal currents of 300 A with testing values of up to 2000A. The scales allow testing of 3rd party devices as well. The synchronous chronoscope came with microswitches (±6 ms) for exact measurement. To allow easy transport and operation the device was divided into 3 portable units. A dolly could be used for transport.

Programma in Sweden started in 1980 producing the famous SVERKER 608 (Figure 2, table 1) for testing where variable current and voltage are required. Application examples have been current relays, voltage relays, time and power relays. Additional use cases have been measuring of current transformers, ratio tests and plotting of magnetizing curves.
ABB produced the modular static generator protection system GSX5e in 1981.  All static relay modules are equipped with test button. This allowed testing the electronics of the relay as well as the functionality of the module. There was one “floor” in the rack used for testing purposes. It was equipped with currents (3A; 15 A). voltages (20V; 110 V and 220 V) and allowed to have 100 V with a phase angle of 90° against the current. The name of the testing floor was GSZ120. This testing system allowed testing (by injecting) of the single protection as well the entire cubicle and its wiring. There was even an opportunity for automated testing. The GSZ1000 is testing the relays in sequences. It is checking startup values and operation times of the relays. They are programmed and compare with the specified value. (Figure 3).

Developing static protection at SIEMENS also resulted in stationary test sets in 1986. The 7VP22 und 7VP23 could be used to test a large amount of centralized protection elements. The special application is the machine protection unit built in the cubicle. The testing includes connections to instrument transformers, protection devices and auxiliary elements, as well as tripping circuits and circuit breaker coils. Possible faults within the machine could be replicated on the secondary side. The testing itself will run automatically. The tripping circuits will be interrupted in this moment for a very short time only – the operating time of the protection. The 7VP22 (Figure 5 and table 2) was used for supervising 9 tripping circuits. The 7VP23 was ready to do so with 18 circuits. It came with a visualization of the operating time.

The German Railway is using 15 kV voltage with 16 ⅔ Hz. This requires special protection systems like the SDB15 (AEG). Additionally, they do not just switch off the fault in case of a short circuit- they test if the fault is still existing afterwards over a resistance before switching on again.  Additionally, they had built in test devices- AEG presented such a device in 1982 - the SDB15C (Figure 6).  With the current delivered, different functionalities such as tripping, and indication could be checked. For each feeder a single testing device was built in. This allowed adaptation to the settings of the different feeders. A test transformer 220 V/ 24 V with 16 2/3 Hz with fuse delivered the testing voltage of 24 V. This was available only once but shared within the cubicle with ring connection. In every test device a switch was built in to allow the test. An interlocking guaranteed that only one feeder was tested at the same time.
Additionally, the railway applies “superior protection” (Ü-Schutz) to protect the entire station. In 1983 AEG presented the SDB401 (Figure 4).

It realizes the backup protection for transformer and line protection. It was also built in the INTERMAS-System (6 units). In another rack (3 HE) the equipment EPZ830 for testing the protection was built in. The weight of the rack with protection was 20 kg, while the test rack was 8 kg.






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