Integrated Protection Set — Relay with LPCT and LPVT
Relay, current sensor and voltage sensor matched as one chain
Buying a relay, a current transformer and a voltage transformer separately means owning the interface between them. Burden has to be matched, the accuracy budget is the sum of three data sheets, and the panel has to hold three devices. The integrated protection set removes that work: a digital protection relay is supplied matched with electronic low-power current transformers (LPCT) and low-power voltage transformers (LPVT), pre-engineered as one protection and metering chain.
The set covers 17.5, 24 and 36 kV maximum voltage (the 15, 27 and 38 kV ANSI classes), with power-frequency withstand of 34, 50 and 70 kV and basic impulse levels of 95, 125 and 170 kV at 60 Hz. Ten analog input channels hold 30 days of history, up to 100 waveforms are stored, and harmonics are monitored to the 11th order, so fault records, load profile and power quality analysis come from the same device. Sensor technology follows IEC 61869-10 for the LPCT and IEC 61869-11 for the LPVT, with ANSI device function numbering in the relay.
Why it matters
Low-power sensors take current transformer saturation and voltage transformer ferroresonance out of the protection chain, which removes two of the classic causes of a misoperated feeder.
One supplier and one accuracy budget mean there is no burden mismatch to reconcile between the relay and the transformer at commissioning.
The set is substantially smaller and lighter than a conventional relay plus CT plus VT assembly, which is what makes a retrofit possible in a panel with no spare depth.
Fault records, a 30-day load profile across 10 analog channels, and harmonic analysis to the 11th order come from the same device, not from a second metering package.
Ratings
Maximum voltage: 17.5 / 24 / 36 kV (15 / 27 / 38 kV ANSI classes)
Power-frequency withstand: 34 / 50 / 70 kV
BIL: 95 / 125 / 170 kV
Frequency: 60 Hz
Waveform storage: Up to 100 waveforms
Harmonics: Monitored to the 11th order
Analog inputs: 10 channels with 30 days of history
Content: Digital protection relay supplied matched with electronic low-power current and voltage transformers, pre-engineered as one protection and metering chain
Standards
ANSI device functions
IEC 61869-10 (LPCT)
IEC 61869-11 (LPVT)
IEC 60255-21
Applications
New MV switchgear designs
Compact and modular substations
Retrofits where panel space is the constraint
Digital substation pilots
Questions engineers ask
What is the advantage of LPCT and LPVT over conventional instrument transformers?Low-power sensors do not saturate the way an iron-core current transformer does, and they do not support ferroresonance the way an inductive voltage transformer can. They are also far smaller and lighter. Because the relay and the sensors are supplied matched, there is no burden calculation to reconcile and one accuracy budget covers the whole chain.
Which voltage classes does the integrated protection set cover?Maximum voltage options are 17.5, 24 and 36 kV, corresponding to the 15, 27 and 38 kV ANSI classes. Power-frequency withstand is 34, 50 and 70 kV respectively, and basic impulse level is 95, 125 and 170 kV. Rated frequency is 60 Hz. Sensor performance follows IEC 61869-10 and IEC 61869-11.
Technical documentation
Download HVEX Protection Set - Relay with Electronic CTs and VTs datasheet (English, PDF)
