LPIT
Low-power instrument transformer LPIT for gas-insulated switchgear, combined LPVT + LPCT in one GIS cast resin partition, 145 / 170 kV insulation levels, IEC 61850-9-2 digital output
LPIT
- One device for all protection and metering: LPVT (capacitive voltage sensors) + LPCT (Rogowski coils) fully compliant to the IEC 61869 series, integrated in a single GIS cast resin partition
- No saturation (unlike conventional CTs), no ferro-resonance effects (unlike conventional VTs) and a wide frequency range measuring harmonics up to the 50th harmonic frequency
- Smaller size and weight of the GIS, easy connection, lower cabling and wiring effort and less insulation gas in the switchgear thanks to the small passive sensors embedded in the cast resin
- Excellent overvoltage performance — no need for disconnection during GIS or HV cable tests, and no hazardous overvoltage at open LPIT terminals
- Rated primary current and voltage settings flexibly defined and modified in the merging unit at any project phase and afterwards — the GIS remains flexible for future increases of nominal current
- Choice of two tested merging units — SIPROTEC 5 6MU85 (IO240 also pluggable directly into SIPROTEC 5 relays) and SEL-700MU with LPIT sensor input card; differential protection schemes using both LPITs and conventional CTs are possible
Protection and metering in gas-insulated switchgear (8DN8, 8VN1)Digital substations with IEC 61850-9-2 process busDifferential protection schemes combining LPITs and conventional CTsPower-quality monitoring with harmonics measurement up to the 50th harmonic
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LPIT covers up to 170 kV of the gas-insulated switchgear range (≤ 550 kV across the category, √ scale).
Specifications
Main
| Product family | Low-Power Instrument Transformer (LPIT) for gas-insulated switchgear |
| Type | Combined Low Power Voltage Transformer (LPVT) and Low Power Current Transformer (LPCT) in one device, integrated in a GIS cast resin partition |
| Sensor principle | Rogowski coils for current, capacitive voltage sensors — passive sensors embedded in the cast resin |
| GIS integration | LPIT-145 for 8DN8 and 8VN1 GIS; LPIT-170 for 8DN8 GIS |
| Digital output | IEC 61850-9-2 Sampled Values via merging unit (SIPROTEC 5 6MU85 or SEL-700MU) |
| Applied standard | IEC 61869 |
General ratings
| Rated insulation level | 145 / 275 / 650 kV (LPIT-145); 170 / 325 / 750 kV (LPIT-170) |
| Rated frequency fr | 50 Hz / 60 Hz |
| Rated short-time thermal current Ith | 50 kA (3 s) LPIT-145; 63 kA (3 s) LPIT-170 |
| Temperature range | -30 °C / +55 °C |
| Weight | 100 kg (LPIT-145 for 8DN8); 185 kg (LPIT-145 for 8VN1 and LPIT-170 for 8DN8) |
| Measurement of harmonics | up to the 50th harmonic frequency |
LPCT — current sensor
| Rated primary current Ipr | 200 A |
| Rated accuracy class | 0.2S / 5P250 / 2TPM (LPIT-145, 8DN8); 0.2S / 5P200 / 2TPM (LPIT-145, 8VN1); 0.2S / 5P315 / 2TPM (LPIT-170, 8DN8) |
| Rated extended primary current factor Kpcr | 15.75 (LPIT-145); 20 (LPIT-170) |
| Rated symmetrical short-circuit current factor Kssc | 250 (LPIT-145); 315 (LPIT-170) |
LPVT — voltage sensor
| Rated primary voltage Upr | 66 to 138 / √3 kV (LPIT-145); 66 to 154 / √3 kV (LPIT-170) |
| Rated accuracy class | 0.2 P |
| Rated voltage factor FV and permissible duration | 3 / 2000 h |
Merging units & digital interface
| Tested merging units | SIPROTEC 5 6MU85 with dedicated LPIT input card (IO240 also pluggable directly into SIPROTEC 5 relays); SEL-700MU with LPIT sensor input card (redundant voltage measurement possible) |
| Process bus interface | IEC 61850-9-2 and IEC 61850-9-2 LE |
| SCADA communication | IEC 61850-8-1 and other protocols |
| Breaker control | IEC 61850 GOOSE |
| Time synchronization | IEEE 1588v2 / PTP |
| Interoperability | Standardized in IEC 61869-9 / -13 and IEC 61850 Ed. 2.1 |
Options & variants
The three columns reproduce the General / LPCT / LPVT ratings table on page 2 of the 03.2024 product flyer verbatim. Rows identical across all three variants (rated frequency 50/60 Hz, temperature range -30 °C / +55 °C, harmonics up to the 50th, applied standard IEC 61869, LPCT Ipr 200 A, LPVT accuracy class 0.2 P, voltage factor 3 / 2000 h) are kept in the spec groups above. No order-data-derived variants exist for this family.
| Variant (GIS type) | Rated insulation level | Ith (3 s) | Weight | LPCT rated accuracy class | Kpcr / Kssc | LPVT rated primary voltage Upr |
|---|---|---|---|---|---|---|
| LPIT-145 (8DN8) | 145 / 275 / 650 kV | 50 kA | 100 kg | 0.2S / 5P250 / 2TPM | 15.75 / 250 | 66 to 138 / √3 kV |
| LPIT-145 (8VN1) | 145 / 275 / 650 kV | 50 kA | 185 kg | 0.2S / 5P200 / 2TPM | 15.75 / 250 | 66 to 138 / √3 kV |
| LPIT-170 (8DN8) | 170 / 325 / 750 kV | 63 kA | 185 kg | 0.2S / 5P315 / 2TPM | 20 / 315 | 66 to 154 / √3 kV |
Documents & downloads
Flyer Low-Power Instrument Transformer (LPIT) — Technology for Protection and Metering (flyer, 03.2024)
Also covered in the technical library
Presentation Low-Power Instrument Transformers (LPIT) for High-Voltage GIS — Sales Presentation
Ordered designations
Representative orderable type designations of this family — searchable via the catalog search.
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