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Zelisko sensors were specially developed for high-precision voltage measurement according to IEC 61869 in medium-voltage switchgear. The key benefit offered by Zelisko’s voltage, phase current, earth fault, multi-function and combined sensors is a blend of high-precision measurement with straightforward installation and maximum reliability.
The sensors function perfectly in virtually any temperature range, and can be easily and quickly retrofitted without major modifications to switchgear or grid infrastructure.
They can operate at voltages up to 72kV with rated currents of up to 50kA.

Voltage Sensor

The voltage sensor is mounted on the cable outlet at the back of the T-connector. Therefore, the insulating plug is replaced by the voltage sensor. The accuracy of the sensor, i.e. the absolute value error and phase error, is constant over the lifetime and have not to be re calibrated or readjusted. The calibration to the desired nominal and secondary voltage is performed at Zelisko. Cable length in delivery condition may not be changed. The voltage sensor is suitable for both, original equipment and retrofitting, without any reconstructions of network stations necessary.

Rated Primary voltage : Upto 72.5 kV
Rated secondary voltage : 3,25/√3 V (or on request)
Standard : IEC 60044-7

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Current Sensor

The phase current sensors are available in different versions, first, in the version with dividable ring core for retrofit purpose. In addition, the sensor is available with closed ring cores for original equipment.
- SMCS-JW1001 (closed core) - This type is designed for simple original equipment in switchgears. It is slide on the not mounted output T-connector in the substation.
- SMCS/T-JW1002 (split core) - The retrofit application in existing installations is the primary field of application for this type. The click system enables a tool-free mounting of the sensor on site. 

Rated Primary voltage : 300 A; Ext. 200% (or on request)
Rated secondary voltage : 225 mV according to IEC 60044-8
Standard : IEC 60044-8

Sensors for
Earth Fault Detection

The sensor for earth fault detection of type GAE120/SENS is based on a market proven and established product. All output cables of the substation are conducted through this transformer. In case of earth fault in a three-phase network, a current occurs due to the displacement of the neutral point. This current is implemented with a specific ratio in the output of the sensor. Therefore, the system enables to detect fault and short-circuit currents, respectively.

Ratio earth fault detection : 60 A // 225 mV (or on request)
Rated secondary voltage :
225 mV according to IEC 60044-8
Standard : IEC 60044-8


Measuring amplifier - VMA

VMA Voltage Metering Amplifier - MORE FLEXIBILITY FOR METERING IN MEDIUM-VOLTAGE POWER GRIDS. The Zelisko VMA is an active high-precision voltage amplifier with 3 channels. In combination with Zelisko low-power voltage sensors it converts the output voltages from 3.25/√3 V to 100/√3 V or 110/√3 V. An easy integration of LPVT technology with existing equipment directly supports the modernization of power-grids. Extended compatibility is achieved through amplification of the Zelisko sensors’ secondary
output voltage. This allows the usage of energy meters or other measurement appliances designed for signal levels of conventional instrument transformers.

Combi-Bushing Sensor (Bushing Type)

Smart Sensor All in One Technology Indoor combined low power instrument transformer bushing SMVS- UWxxxx,
- Voltage, Current Sensor Combined Monitoring (Bushing Type).

- Up to 36kV for automated RMU´s 
- According IEC-61869 Instrument Transformer Standard
- Capacitive-Divider for VDS System LRM according to IEC 61243-5

Contact us for more Information


Outdoor - Combi Sensor

This outdoor sensor combines functions of a voltage and a current
sensor in one design. Due to the structural shape and use of cycloaliphatic epoxy resin, it is adapted for outdoor application.
The combined sensor is available with an insulation level up to 36 kV.
By usage of proven Zelisko sensor-technology, specified accuracy
class can be guaranteed for the complete lifetime without calibration on site.


Rated Voltage  : max. 30/√3 kV
Rated current : 300 A (or on request)
Rated secondary voltage : 3,25 / √3 V (or on request)
Rated secondary current : 225mV
Standard : IEC 60044-7, IEC 60044-8

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