IEC 61869 –10 AND IEC 61869 –11 PASSIVE SENSORS AND THEIR INTERFACE WITH IEDS

Abstract

The International Electrotechnical Commission standard IEC 61869 – 10/11, applicable to newly manufactured AC low-power instruments transformers (LPIT), replaces the old IEC 60044 –7/8 (published in 1999) in the applicable parts that are common to the passive sensors. IEC 61869 – 10 /11 standards (Additional requirements for low-power current and voltage transformers) together the more general IEC61869–6 (Additional general requirements for low-power instrument transformers) define the main characteristics and requirements of the Low power Current transformers (LPCT) and Low Power Voltage Transformers (LPVT) which are going to be connected to a SAMU (Stand Alone Merging Unit), defined in IEC 61869–13, or directly to a Protection Control and Metering Device. When no intermediate merging unit is connected between the sensors and the electronics, the IED must be prepared to receive the usually very low level analogue signals that sometimes come from the relatively far passive LPITs, which at the same time are connected to the MV lines where high voltage and current are present. The connection between both devices, sensors and IED, must be appropriate so as not to affect the low voltage levels present. The effect of the load impedance (burden), the connection cables and the electronic input stages on the total characteristics due to possible interferences and couplings are discussed in the paper. The paper explains the main points of the standard IEC 61869, emphasizing in the IEC61869-11 part and those points related to connections, impedances, and accuracy, including harmonics and frequency response. The article also talks about some design factors which affect both sensors and the electronic devices connected to them. Finally, the paper also shows the results obtained from the mentioned tests on different voltage sensors and the performance results under fault condition when working together with a ZIV Protection, Control and Metering device.