Testing and Measuring Instruments

LET-400-RD primary test equipment

It allows to perform with sufficient power, all the primary current injections to test the proper function and wiring of all the elements that compose the protection and measuring section in a substation.
The regulation system is based on a continuously variable autotransformer (Variac) that supplies to a power transformer that delivers the high current outputs and isolate the main supply from the load. A built-in ammeter and a timer gives the information about the current value and the operation time of the relay or breaker under test.


  • Permanent current up to 400A 1KVA in 4 Ranges.
  • Built in digital ammeter 0.5% accuracy.
  • Built in digital timer resolution 1 ms.
  • Thermal and shortcircuit protection.


  • Test of the I/T curve in primary current relays test.
  • Primary injection tests.
  • Test of measurement and protection transformers.
  • In general, primary injection tests including the complete loop, such as current transformer cables, protective relays, and circuit breakers.