Research And Application Of The Real-time Alarm Of PT Multi-point Grounding

The voltage transformer in high voltage power system in time according to a certain ratio down to 100 V or lower level of two times the standard voltage for relay protection,control and measuring instrument device.In order to ensure the fault on the power system will be an accurate voltage transmission to two side,at the same time to prevent the one or two voltage transformer insulation breakdown,high voltage through the two side,resulting in personal injury and equipment damage,voltage transformer must take place.GB/T14285-2006 "Regulations" for relaying protection and security automatic equipment and "relay protection and anti accident measures in power system elements" are clearly defined,the two circuit for voltage transformer control room zero phase busbar connected N600(hereinafter referred to as the PTN600),only in the control room grounding point.Total net transfer under the South has issued "on the prevention of power plant substation protection voltage transformer secondary circuit two grounding point of the notice",clearly requires the two loop voltage transformer according to the following principles: "several groups of grounding voltage transformer secondary circuit two with zero phase busbar connected control room the only in the control room will be one point grounding for the voltage level are respectively connected to the case,must ensure that the voltage transformer secondary circuit two the voltage level of the room without any contact".At the same time,the request for 6 months to detect a N600 grounding current,and the limits of 50 mA and 20 mA value as a basis to determine the existence of multi point grounding fault PT.However,in the actual operation,due to the design,construction,transformation and aging of the two equipment,insulation breakdown and other reasons,may cause the voltage transformer in the two circuit multi-point grounding.When the grounding fault occurs in the substation and the line outlet,or the lightning strikes,the grounding grid flows through a large current,and the high potential difference between the 2 distances is very high.The actual flow of voltage protection device is two times the actual voltage superimposed voltage transformer the differential pressure,the voltage phasor of the superimposed cannot reflect a voltage amplitude and phase of normal,normal working condition will damage the protection action,serious interference protection,protection may lead to malfunction and refuse.At the same time,with the transformation of the primary equipment of the substation,the grounding point of the PT two circuit is also increasing,which leads to the occurrence of PTN600 multi-point grounding fault in the power grid.At present our country in PT multi point grounding protection misoperation caused by more research,just published papers,the research hotspot in PT multi point grounding analysis of causes of misoperation of protection and puts forward some preventive measures,and realize the PTN600 multi-point real-time alarm grounding fault detection and fault location there is no device.This paper studies the PTN600 multi point principle,multi point grounding,grounding effect and relay protection device the grounding point of the grounding current and PT multi point grounding fault form,design a single-phase current signal injection PTN600 multipoint grounding monitoring and fault finding new based on a detailed analysis of the principle of this method,the influence of power grid operation and fault point of detection method,and designs a set of real-time alarm PTN600 multi point grounding detection device based on the detection method.Using this device,no need to remove N600 grounding wire,through the signal current injection detection to realize the PT multi point grounding fault judgment,instead of manual real-time monitoring and warning,improve work efficiency,realize the PTN600 multi point grounding real-time monitoring,and implementation of PTN600 multi point search and locate the fault point of the ground,the maintenance personnel more quickly eliminate multi point grounding.Finally,the test results show that the device can detect whether there are multiple faults in the PTN600 in real time,and can give alarm prompt in time.