Overview

This Technical Report of IEC 61869 series provides technical information for understanding the undesirable phenomenon of ferroresonance oscillations in medium voltage and high voltage networks in connection with inductive voltage transformers. Ferroresonance can cause considerable damage to voltage transformers and other equipment. Ferroresonance oscillations may also occur with other non-linear inductive components. Ferroresonance refers to non-linear oscillations that can occur in power systems where inductive components with a ferromagnetic core, together with capacitances and an AC voltage source comprise a system capable of oscillation. During the last twenty years ferroresonance oscillations in substations with inductive voltage transformers according to IEC 61869-3 or with combined transformers according to IEC 61869-4 were discussed in the international Cigré working groups and in IEEE committees in the US. The results were published in Cigré technical report or IEEE publications. The reasons for these publications were the more frequent occurrence of ferroresonance oscillations in substations. As a consequence of the price pressure on the operating authorities and the component manufacturers such as instrument transformers, power transformers and grading capacitors for high-performance circuit breakers have led to an increasingly higher exploitation of the system and components with the following side effects: - the shift from normal rated voltage (U_pr) in the direction of the maximum permitted highest voltage for equipment (U_m) (IEC 60071-1); - increasing the flux density by reducing the cross-section of the core of the inductive voltage transformer; - reduction of the substation capacitance by using new components (for example MV and HV instrument transformers) and as a result increase of the excitation-voltage for the non-linear circuits; - reduction of the actual burden in the substation by using digital meters and relays with burden of approximately 1 VA, while still specifying the high nominal burden (50 VA to 400 VA) for the inductive voltage transformer. However, even these higher burdens are often not sufficient to prevent ferroresonance oscillations. The IEC Technical Report IEC/TR 61869-102:2014 on which this VDE Technical Report is based is a document (Technical Report) which has been published for the first time in this form in parallel to the standard series IEC 61869 dealing with the topic ferroresonance oscillations in substations with inductive voltage transformers. The summarized information provides both indications on the theoretical background of this phenomenon as well as examples from real substation configurations and provide practical corrective measures. In addition to the required references to the various parts of the standard series IEC 61889, this document also provides numerous indications dealing with this topic. IEC Technical Reports are not being harmonized in Europe. For this reason the national Working Committee K 471 ("Instrument transformers") has decided to publish this document to the instrument transformer standard series IEC 61869 as a VDE guideline within the standard series DIN EN 61869 (VDE 0414-9) in order to also provide the users with a German version on this topic. 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