Overview

This part of IEC 61869 has been prepared as Technical Report. It is applicable to inductive and electronic instrument transformers with analogue or digital output for use with electrical measuring instruments for measurement and interpretation of results for power quality parameters in 50/60 Hz a.c. power supply systems. Until now instrument transformers are used for measurement and protection purposes and provide a secondary signal with the required accuracy which is suitable for protection relays and measurement equipment. Nowadays there is a growing need for inspection of the parameters of electric energy at a certain point of an energy supply system, in other words the demand for the measurement of the voltage quality (Power Quality, PQ) on this location of the system. This Technical Specification serves for the provision of the currently available relevant information on this topic. After specification of the upcoming problems and the aspects to be inspected, indications for the methods and arrangements to be applied are given. The influence of instrument transformers on measurements of the voltage quality is linked to the applied technique, design and manufacture. Instrument transformers are applied to provide a measurement device for measurement of the power quality with a signal which is suitable for their input channels and contains all corresponding information required by the primary signals. This information may be the exact reproduction of the primary signal or it can provide the measurement device with the corresponding information to restore the power quality parameters of the primary signal. Inductive instrument transformers have so far been developed with a mainly linear behaviour in the range of amplitudes of the primary signal and rated mains frequency: outside these ranges their behaviour is not standardized, even if their linearity characteristic values can reach beyond the rated ranges. Inductive instrument transformers may however not be considered linear, neither when the amplitude of the primary signal nor the amplitude of the frequency changes; this fact so far concerns the description of the instrument transformer then the measurement behaviour. Due to procedural constraints there is currently no standardized laboratory procedure which is suitable for inductive instrument transformers for these purposes. In practice such tests did not yet belong to the scope of the standard laboratory equipment and new, specialized test set-ups shall be developed to re-evaluate the behaviour properly. Furthermore additional information can be supplied from field tests, comparative measurements with inductive instrument transformers and from data from sensors described exclusively as linear. On the current stage of development technical literature provides many articles regarding the frequency response of instrument transformers. This information can be helpful for the evaluation of the behaviour of instrument transformers for measurement of parameters of the power quality, but they can be also misleading, as they are probably not representative for the actual behaviour of the sensor at higher voltages and currents. For this reason this Technical Specification does not deal with information for the frequency response of instrument transformers and the measurement behaviour in different clauses. The parameters considered in this Technical Report include power frequency, voltage magnitude, flicker, supply voltage dips and swells, voltage interruptions, unbalance, voltage and current harmonics and interharmonics, mains signalling on the supply voltage and rapid voltage changes ((Figure)) Voltage transformer technologies frequency range ((Figure)) Current transformer technologies frequency range. The responsible committee is K 471 "Messwandler" ("Instrument transformers") of the DKE (German Commission for Electrical, Electronic and Information Technologies) at DIN and VDE.

Document: references other documents

Responsible national committee

DKE/K 471 - Messwandler