Sensor part for installation in medium-voltage cable compartments and a device for measuring a voltage in medium-voltage circuits comprising such sensor part
Sensor part for installation in medium-voltage cable compartments, which sensor part comprises a voltage divider based on the capacitive divider principle, which voltage divider comprises: —a first capacitor, comprising an elongate primary conductor wrapped in a dielectric material and an elongate conducting shield arranged around the dielectric material, which first capacitor has a first capacitance rating; —a second capacitor, having a second capacitance rating, which second capacitor further comprises a first lead conductively connected with the conducting shield of the first capacitor and a second lead conductively connected to a common reference, such as earth; —a voltage output line, conductively connected with the conducting shield of the first capacitor; wherein the second capacitance rating is larger than the first capacitance rating, so that when during use the primary conductor is conductively connected with a live circuit carrying an alternating current, a measurement of a voltage between the common reference and the voltage output line can be taken as a ratio of the voltage between the live circuit and the common reference.
1. A device for measuring a voltage in medium-voltage circuits, the device comprising:
sensor part for installation in medium-voltage cable compartments, which sensor part comprises a voltage divider based on the capacitive divider principle, which voltage divider comprises:
a first capacitor, comprising an elongate primary conductor wrapped in a dielectric material and an elongate conducting shield arranged around the dielectric material, which first capacitor has a first capacitance rating, wherein a part of the primary conductor enclosed by the conducting shield forms a first capacitance plate of the first capacitor and the conducting shield forms a second capacitance plate of the first conductor;
a second capacitor, having a second capacitance rating, which second capacitor further comprises a first lead conductively connected with the conducting shield of the first capacitor and a second lead conductively connected to a common reference, such as earth; and
a voltage output line, conductively connected with the conducting shield of the first capacitor;
wherein the second capacitance rating is larger than the first capacitance rating, so that when during use the primary conductor is conductively connected with a live circuit carrying an alternating current, a measurement of a voltage between the common reference and the voltage output line can be taken as a ratio of the voltage between the live circuit and the common reference,
wherein the sensor part further comprises a temperature sensor with a temperature output line, arranged in heat conducting connection with the first capacitor for measuring the temperature of the first capacitor, and
wherein the device further comprises a converter part, which converter part comprises a controller for applying a temperature correction to a voltage measurement taken between the voltage output line and the common reference, which controller comprises a corrected voltage signal determined by taking the voltage measurement and applying a correction based on a temperature measurement taken from the temperature output line, for compensating for temperature related variation of the first capacitance rating,
wherein the converter part comprises a cascade of comparators to apply a correction factor depending on in which temperature range the temperature measurement is.
2. The device according to claim 1 , wherein the dielectric material further extends radially from the conducting shield forming an insulating housing or bushing.
3. The device according to claim 1 , wherein the temperature sensor is arranged within the dielectric material.
4. The device according to claim 1 , wherein the ratio of the first capacitance rating and the second capacitance rating is approximately 1:300, 1:220 or 1:85, for bringing respectively 35 kV, 26 kV or 10 kV within a safe measuring range of 0-120V.
5. The device according to claim 1 , wherein the sensor part further comprises:
a current output line;
a printed circuit board Rogowski current sensor comprising a Rogowski coil, wherein the Rogowski coil is conductively connected with the current output line.
6. The device according to claim 5 , wherein the temperature sensor is arranged in heat conducting connection with the Rogowski coil, for measuring the temperature of the Rogowski coil.
7. The device according to claim 5 , wherein the controller further comprises a corrected current signal determined by taking a secondary current measurement between the current output line and the common reference and applying a correction based on a temperature measurement taken from the temperature output line, for compensating for temperature related variation of the Rogowski coil voltage.
8. The device according to claim 1 , wherein the controller comprises updatable firmware for storing and adapting temperature related corrections.
9. The device according to claim 1 , wherein the converter part further comprises a communication port for receiving firmware and/or communicating the corrected voltage signal or the corrected current signal.