Flyer · EN — Three-page flyer introducing Siemens Energy Low-Power Instrument Transformers (LPITs) for gas-insulated switchgear: combined low-power current (Rogowski coil) and voltage (capacitive sensor) measurement integrated in a single GIS cast resin partition, with digital IEC 61850-9-2 Sampled Values output via a choice of two merging units (SIPROTEC 5 6MU85 or SEL-700MU). Includes the full ratings table for the three variants LPIT-145 (8DN8), LPIT-145 (8VN1) and LPIT-170 (8DN8).
Siemens Energy LPITs are innovative low power current and voltage transformers providing a safe, reliable and standardized solution for measurement and protection applications in GIS. Without saturation nor ferro-resonance phenomena, the LPIT delivers a digital output signal according to IEC 61850-9-2, with a choice of two merging units: SIPROTEC 5 and SEL-700MU.
The LPIT combines a Low Power Voltage Transformer (LPVT) and a Low Power Current Transformer (LPCT), fully compliant to the IEC 61869 series of standards, in one device. The measurement is based on Rogowski coils for current and on capacitive voltage sensors. Both sensors are integrated in the same GIS cast resin partition.
Smaller size and weight of the GIS due to the small dimensions of the sensors and their integration into a GIS partition. Easy connection and lower cabling and wiring effort. High reliability and long lifetime due to the robust design of the passive sensors embedded in the cast resin. Less insulation gas in the switchgear.
Excellent overvoltage performance — no need for disconnection during GIS or HV cable tests — and no hazardous overvoltage at open LPIT terminals. A single LPIT covers all protection and metering requirements and, thanks to its linearity, also a wide range of primary currents and voltages, simplifying stock management, engineering and logistics.
Settings for rated primary current and voltage can be flexibly defined and modified in the merging unit at any phase of the project and afterwards; in this way the GIS remains flexible for future increases of nominal current.
Furthermore, the LPIT sensors provide improved measurement performance due to high linearity, no saturation (unlike conventional CTs), no ferro-resonance effects (unlike conventional VTs) and a wide frequency range for measuring harmonics up to the 50th harmonic frequency.
Choose between the SIPROTEC 5 6MU85 and SEL-700MU merging units, equipped with a dedicated LPIT input card and tested by Siemens Energy. When using SIPROTEC 5 relays, the IO240 can also be plugged directly into the relay.
Merging units provide the standardized Sampled Values digital output, allowing the LPIT to seamlessly interface with IEC 61850-9-2 compatible protection relays. Differential protection schemes using both LPITs and conventional CTs are possible.
Merging-unit benefits: minimized wiring by local installation (e.g. inside the LCC); easy extension — simply connect a new device to the process bus and get instant access to the measured values; maximum network reliability through seamless redundancy protocols; interoperability ensured, standardized in IEC 61869-9/-13 and IEC 61850 Ed. 2.1.
Digitalization of all primary data close to the process; low energy analog inputs (LEA) for GIS LPIT sensors; scalable number of binary inputs and outputs; process bus interface according to IEC 61850-9-2 and IEC 61850-9-2 LE; seamless redundancy protocol support; breaker control via IEC 61850 GOOSE; SCADA communication via IEC 61850-8-1 and other protocols; time synchronization via IEEE 1588v2/PTP; redundant voltage measurement possible with SEL-700MU.
Ratings for the three LPIT variants as stated in the flyer. LPIT-145 variants are available for 8DN8 and 8VN1 GIS; LPIT-170 for 8DN8 GIS.
| General | LPIT-145 (8DN8) | LPIT-145 (8VN1) | LPIT-170 (8DN8) |
|---|---|---|---|
| Rated insulation level | 145 / 275 / 650 kV | 145 / 275 / 650 kV | 170 / 325 / 750 kV |
| Rated frequency fr | 50 Hz / 60 Hz | 50 Hz / 60 Hz | 50 Hz / 60 Hz |
| Rated short-time thermal current Ith | 50 kA (3 s) | 50 kA (3 s) | 63 kA (3 s) |
| Temperature range | -30 °C / +55 °C | -30 °C / +55 °C | -30 °C / +55 °C |
| Weight | 100 kg | 185 kg | 185 kg |
| Measurement of harmonics up to | 50 | 50 | 50 |
| Applied standard | IEC 61869 | IEC 61869 | IEC 61869 |
| LPCT — Rated primary current Ipr | 200 A | 200 A | 200 A |
| LPCT — Rated accuracy class | 0.2S / 5P250 / 2TPM | 0.2S / 5P200 / 2TPM | 0.2S / 5P315 / 2TPM |
| LPCT — Rated extended primary current factor Kpcr | 15.75 | 15.75 | 20 |
| LPCT — Rated symmetrical short-circuit current factor Kssc | 250 | 250 | 315 |
| LPVT — Rated primary voltage Upr | 66 to 138 / √3 kV | 66 to 138 / √3 kV | 66 to 154 / √3 kV |
| LPVT — Rated accuracy class | 0.2 P | 0.2 P | 0.2 P |
| LPVT — Rated voltage factor FV and permissible duration | 3 / 2000 h | 3 / 2000 h | 3 / 2000 h |
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