EE-501 ( Parallel Control Unit)

Controllers for Parallel Transformers EE-501

Parallel Control Unit The Parallel Control Unit (PCU) is used for controlling 2 Transformers in parallel. Raise & Lower contacts from AVR1 & AVR2 are connected to PCU, and the outputs from PCU are connected to OLTC1 & OLTC2. Switches on the front panel allows selecting AVR1 or AVR2 as master & the other as follower, or both as masters (independent). Selecting both AVRs as follower will block the PCU. Also if the Manual mode is selected, PCU is blocked i.e. no output pulses are given. External A/M switch (NO contacts) are sensed for determining Auto / Manual mode of operation. TPI of both Transformers are displayed on PCU. In Master – Follower mode the tap no. of Follower is made equal to the tap no. of Master. If the Tap nos. of both the Transformers are unequal for 5 Min., both the OLTCs are blocked.


  • Built-in Tap Position Indicators for both Transformers
  • Micro controller based circuit
  • 4-20 mA Output for both Tap Position Indicators
  • Selectable delay between Master and Follower pulses
  • Switch selectable mode of operation (Master / Follower)
  • Out of step indication and blocking
  • Bus Coupler closure indication
  • Minimum / Maximum Tap blocking


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