Glossary Term: Low Power Instrument Transformers

Acronym: LPIT

Low Power Instrument Transformers (LPITs) are innovative voltage and current transformers that provide a safe, reliable and standardized solution for measurement and protection applications in Gas Insulated Switchgear (GIS).

They can also be used in Air Insulated Switchgear (AIS). Unlike conventional inductive measurement transformers, they do not suffer from saturation effects, or ferro-resonance phenomena.

In High Voltage applications typically LPITs with a digital signal output according to IEC 61850-9-2 / IEC 61869-9 are used and then connected to a digital revenue meter and/or protection relays. In Medium Voltage applications LPITs with analogue low power outputs according to IEC 61869-10 and -11 are commonly used.

LPITs can combine a Low Power Voltage Transformer (LPVT) and a Low Power Current Transformer (LPCT).

In GIS current measurement is typically based on Rogowski coils and voltage measurement is based on capacitive voltage dividers, in AIS also optical LPCTs are used.

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