What is the purpose of CTs and PTs in LV / MV panels?

Electrical
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What is the purpose of CTs and PTs in LV / MV panels?

CT and PT in LV and MV Panel
CT and PT in LV and MV Panel1024×1536 135 KB

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In LV (Low Voltage) and MV (Medium Voltage) panels,

  1. Current Transformers (CTs) and

  2. Potential Transformers (PTs)

are primarily utilized for measurement, protection and electrical isolation.

A Current Transformer (CT) steps down high line current to a lower standardized value (typically 1A or 5A) so that it can be safely measured by instruments such as ammeters and energy meters and also supplied to protection relays for detecting faults like

  1. overloads,

  2. short circuits and

  3. earth faults.

Similarly, a Potential Transformer (PT) also known as a Voltage Transformer (VT) steps down high system voltage to a safe level (commonly 110V or 63.5V) for accurate voltage measurement and for use in protective relays and synchronization systems.

Both CTs and PTs provide isolation between high voltage (HV) power circuits and low voltage (LV) control / metering circuits ensuring safety of equipment and personnel while enabling a accurate monitoring and reliable operation of protection schemes in electrical panels.