differential protection relay of Generator-transformer set is mainly suitable for medium and small generator transformer set differential protection.One generator and one transformer use 9699A generator transformer differential protection,two generator and one transformer use the 9699B generator-transformer set,The generator transformer protection relay is composed completely of 9681 main transformer high backup protection relay and 9689 generator grounding protection relay.
protection function of generator transformer protection relay
Differential instantaneous trip protection,
Proportional differential protection (with two harmonic brake, CT disconnection)
CT line-break alarm
Y/△ Compensation
Non electricity protection－
Hydraulic accidents－trip
Excitation accident－trip.
Electrical accident－trip
BTZWS－trip
BTZWS－alarm
Super high temperature－trip
temperature increment－alarm
Pressure release (throw - trip; back alarm).
Transverse differential protection（Each phase of the generator is protected by a generator consisting of parallel windings.）.
Measurement and control function
High side current：IA、IB、IC；
Low side current：Ia、Ib、Ic；
Differential current：DIa、DIb、DIc；
auxiliary function
Fault recording
communication mode
485communication
Ethernet communication
Optical fiber communication
The action principle of 9699 generator transformer differential protection relay protection
Longitudinal differential instantaneous trip protection
The longitudinal differential instantaneous trip protection is essentially a reflection of the fast motion caused by the current difference on both sides of the generator.Used to ensure that fast operated to trip for a serious fault occurs within the generator or the external side of the transformer on both sides or the CT short circuit .Protective action criterion：
Icd >Isd
among：Icd is the actual differential current between two sides of the same phase CT,Isd is differential instantaneous trip current setting value
Any of the three phases is satisfied Icd >Isd then differential protection act and trip all the switches of the main switch of the main switch
Differential current in practical operation= Id + Iww
Ratio differential protection (with CT line-break blocking function)
The protection of the use of split phase, that is, A, B, C any phase of the protection of the action are exported, the following criteria are in a phase as an example
Rate differential element protection action when the following types are set up at the same time
among：Ｉd、Ｉw is respectively the current of the end and tail of the machine.
Ｉsd is differential instantaneous trip current setting value；Ｉcdqd is differential protection threshold setting value；
Ｉzd is Brake current；
Ｉe is Rated current of generator
Differential protection of ratio braking：
Icd＞Icdqd Icd＞K1*Izd （There is relationship between or）
among：Icd is Differential current，Izd is Brake current，K1 is Ratio brake coefficient.
Icdqd is Differential current threshold constant value Icd＝| Id＋Iw | Izd＝| Id一Iw |／2
Simple calculation in debugging：
If the proportional differential act,then Icd＝| Id＋Iw | > Icdqd；
Also meet：Icd＝| Id＋Iw | > K1*Izd = K1* | Id一Iw |／2
On the formula takes into account the vector calculation, if only the calculation of numerical values. Then the upper inequality is：Icd＝| Id - Iw | > Icdqd；
Icd＝| Id - Iw | > K1*Izd = K1* | Id + Iw |／2
way one：if Id > Iw ；
then satisfied：Id > Iw +Ｉcdqd；Id > Iw*（2+ K1）/（2- K1） Ratio differential act
way two：if Id < Iw ；
then satisfied：Iw > Id +Ｉcdqd；Iw > Id*（2+ K1）/（2- K1） Ratio differential act
CT line-break
In order to prevent the CT line-break, the protection is false action, the device with the software set up the delay CT line-break alarm and instantaneous CT line-break protection function
1) Delay CT line-break alarm,When any phase of the difference is greater than 0.15Ie for more than 10 seconds, the CT signal is sent out, but the differential protection is not locked, which is also a self checking function of the AC sampling circuit of the protection device.
2) Instantaneous CT line-break alarm：In the process of fault measurement, the CT line-break is not performed to satisfy any of the following conditions：
The maximum phase current is less than 0.2Ie before starting and the maximum phase current is greater than 1.2Ie
3) A side current simultaneously meets the following conditions considered to be CT line-break
Only one phase current is zero; the other phase current is equal to the starting current.
Note: the protection of electricity exports are3J（C7、C8）、4J（C9、C10）、5J（C11、C12）；
Non electricity protection exports are 6J（C13、C14）、7J（C15、C16）、8J（C17、C18）；
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