Protection History

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

Relay Testing - Test Sets and testing Technology in the 1970s

In the last issue we described the RED1 by AEG. It was developed at the end of 1960s according to the specification of Weber, AEG, and Kirchoff, ZERA. Further developments have been the RED11 and RED12 by AEG (Table 1).  It was possible to test impedances depending on the angle.
Extensions in RED11 and 12 have been:

  • Built in test switch for changing the impedances (5% steps)
  • Current connections 1A and 5A
  • Built in test switch for changing of direction of fault and magnitude

With this device it was possible to test overcurrent, directional relays and time relays. Also, AEG’s auto recloser relays could be tested.
The fault current flows through resistance R. The voltage is connected and causes a voltage drop. The exact resistance is the core of the test set. The ratio U/I = Z is the impedance set. Unstable currents do not change the ratio since the resistance is constant.
RED12 was used instead of RED11 for testing many relays with 1 A nominal current. Especially in case of smaller impedances the device was more accurate.

In the GDR another device was developed to measure burden of 1A and 5A current transformers.  The “Betrieb für Rationalisierung und Automatisierung (BRA)” presented the device “Bürdenmessgerät BMG69” (Burden measuring device) in 1970. (Figure 2).
ZERA (Western Germany) produced in 1970 the universal load transformers UB501, UB2004 and UB5000 (Figure 3 and table 2). Those transformers have been used to test relays, tripping devices, circuit breakers, line and motor protection.  They could be used for warm up tests as well. They consist of regulating transformer with current transformer. The secondary winding of current transformers is separated to allow the output of low voltage at high currents and high voltages at low currents.

The output current is measured via measurement device. Such a combination of transformers allowed a wide range of voltages and currents to be set up (Figure 3, Figure 4).
For testing electronic generator protection BBC produced two devices in 1971.
Both became a part of the protection systems and could be adapted to various needs of the devices. The difference between both variants is the amount of testing circuits to be tested.

With test equipment YP024a (resp. testing parts QSX406, QSX407) the electronic circuits of the relays including the tripping reed contacts were tested via a DC signal.
With the YP024a (Figure 5) single relays could be tested via a test button. Between the input and the measurement circuit of the relay a DC signal was injected.
The test button interrupts the output circuit.
Test equipment YP030a allows also the test of the incoming values of the relay parts, the tripping circuits and coils.
Also “half-period relays” (Figure 6) came with included test equipment.

Power. Flexible. Easergy.
Protecting your electrical assets? today and tomorrow