RO98460B1

RO98460B1 - Method and apparatus for protecting the triphase electrc networks with isolated or compensated neutral

Info

Publication number: RO98460B1
Application number: RO129614A
Authority: RO
Inventors: Aurel Manea
Original assignee: Institutul De Cercetari Stiintifice Pentru Protectia Muncii
Priority date: 1987-09-02
Filing date: 1987-09-02
Publication date: 1990-02-28

Abstract

Inventia se refera la un procedeu si aparat pentru protectia retelelor electrice trifazate cu neutrul izolat sau compensat. Metoda si aparatul, conform inventiei, se folosesc împotriva punerii la pamânt a unei faze la care tensiunea de deplasare sic urentul homopolar, obtinute de la transformatoare de protectie, sunt transformate în impulsuri dreptunghiulare cu amplificatoare operationale, dupa care cele provenite din curentul homopolar sunt diferentiate si aplicate la intrarea de tact a unuinu marator electronic ce numara numai când faza impulsurilor provenite din tensiunea de deplasare aplicate la intrarea de validare a numaratorului este corespunzatoare, respectiv unghiul de defazaj dintre tensiunile sinusoidale initiale indica existent a unui defect pe linia protejata, realizându-se astfel selectivitatea transversala, dupa numararea unui numar prestabilit de impulsuri, impulsul de iesire al numaratorului aplicându-se unui monostabil care actioneaza un circuit de comanda, prin stabilirea numarului de impulsuri dupa care se actioneaza circuitul monostabil fiind terminata temporizarea la care actioneaza protectia realizându-se prin temporizari diferite diferite stabilite cu un comutator decadic o selectivitate longitudinalaa protectiei.The invention relates to a process and apparatus for protecting three-phase electrical networks with isolated or offset neutral. The method and apparatus according to the invention are used against the earthing of a phase at which the homopolar displacement voltage and the protective transformers are transformed into rectangular impulses with operational amplifiers, then the ones originating from the homopolar current are differentiated and applied to the tact input of the electronic lunar unuin which counts only when the phase of the impulses from the displacement voltage applied at the counter validation input is corresponding, respectively the phase angle between the initial sinusoidal voltages indicates an existing defect on the protected line, thus, the transverse selectivity, after counting a predetermined number of pulses, the output pulse of the counter is applied to a monostable which acts on a control circuit, by determining the number of pulses after which the monostable circuit is activated, the timing at which the actions aza protection being achieved by different different timings established with a decade switch a longitudinal protection selectivity.