motor differential protection relay

 

motor Differential protection relay mainly used in the 10KV、6KV、3KV such differential protection of high voltage motor,The protection device has the differential protection; Proportional differential protection of two harmonic brake、CT line-break locking ratio differential protection、CT line-break alarm such protection function、 adopt to a variety of different capacity of the motor main protection;The protection device is generally used in conjunction with a 973 or 974 motor protection relay,be a complete motor protection;
Motor differential protection relay function
      Differential current instantaneous trip protection,
      Proportional differential protection of two harmonic brake;
      CT line-break locking ratio differential protection;
      CT line-break alarm, 
      auxiliary function  
      Fault recording 
      Measurement and control function   
      IA、IB、IC；Ia、Ib、Ic；DIa、DIB、DIC  such Electrical quantity.
 
Communication mode
      485communication；
Ethernet；
Optical fiber communication
  Sampled data channel
0  Machine end IA phase current、       (1) The tail of IA phase current;
2  Machine end IB phase current、       (3) The tail of IB phase current;
4  Machine end IC phase current,       (5)The tail of IC phase current;
6  Spare,                                (7) reserve; 
8 spare,                                 (9) spare; 
A spare;                                 (B) spare C reserve;
  
The Protective action principle of the 996 Motor Differential current instantaneous trip protection
      Longitudinal differential quick break protection substance to reflect on both sides of the motor current and quick action protection, to ensure in the interior of the motor occurred serious malfunction or motor outer sides of CT fault sometimes rapid action on the trip. Protective operating criterion for：Icd >Isd 
among：Icd is the actual differential current of the two sides of the same phase CT，Isd is differential current setting value;
any one of the three phase meet with the Icd >Isd 
Differential protection is the main switch of all switches.
Differential current in practical operation=  Id + Iww 
 
Ratio differential protection（with ＣＴ line-break Locking function）
      The protection of the use of split phase, that is, B, A, C any phase of the protection actions are exported, the following criteria are in a phase for example. When the following kinds of simultaneous set up the ratio of differential element protection action
 motor differential protection relay.jpg
among：Ｉd、Ｉw respectively is the terminal, the tail current,
Ｉsd is differential setting value；Ｉcdqd is differential protection threshold value；
Ｉzd is Brake current;Ｉe is Rated current of motor
Differential protection of ratio braking:
Icd＞Icdqd    Icd＞K1*Izd   （There is relationship between gate）
among ：Icd is Differential current，Izd is Brake current，K1is Ratio braking coefficient    Icdqd differential current threshold atIcd＝| Id＋Iw |    Izd＝| Id一Iw |／2
 
Simple calculation in debugging:
If the proportional differential action,then Icd＝| Id＋Iw | > Icdqd；
Also meet：Icd＝| Id＋Iw | > K1*Izd = K1* | Id一Iw |／2
On the formula is to take into account the vector calculation, if only the calculation of numerical values,The upper inequality is：Icd＝| Id - Iw | > Icdqd；
Icd＝| Id - Iw | > K1*Izd = K1* | Id + Iw |／2
mode 1：if Id > Iw ；
then meet with：Id > Iw +Ｉcdqd；Id > Iw*（2+ K1）/（2- K1）Ratio differential action;
Mode 2：if Id < Iw ；
then meet with：Iw > Id +Ｉcdqd；Iw > Id*（2+ K1）/（2- K1）Ratio differential action; 
 
CT line-break
      In order to prevent CT following line, protection misoperation, 996 motor differential protection device software set delay CT disconnection alarm and instantaneous CT disconnection interlock protection function. 1) delayed CT disconnection alarm: when any phase flow is larger than 0.15Ie time exceeds 10 seconds a CT disconnection alarm signal, but not blocking differential protection. This also and Protective Relay AC sampling circuit self-test function. 2) instantaneous CT disconnection alarm: in fault measurement program, meet either of the following conditions without the CT disconnection discrimination: before starting a side of the maximum phase current is less than 0.2Ie; moving from the maximum The phase current is greater than 1.2Ie. 3) while the side current meets the following conditions, it is considered that the CT disconnection: only one phase current is zero; the other phase current is equal to the starting current. 
 
Non electricity protection
      Hydraulic accident, exciter accident, electrical accidents respectively corresponding into R3, R4, R5 when the back of the protection, corresponding to the input amount input signal, alarm, drive signal relay 12j (C2 / C3); when cast protect, corresponding to the input amount input signal, accident, protect exports are 6J（C13/C14）、7J（C15/C16）、8J（C17/C18）
Note: the protection of electricity exports are 3J (C7, C8), 4J (C9, C10), 5J (C11, C12); non electricity protection exports are 6J (C13, C14), 7J (C15, C16), 8J (C17,) (, C18);