How 86G & 86T Relay works ??

86 G (Generator Lockout relay):-

1.      59 G= Generator O/V                                                     =110 % Alarm &120% Trip within0.05 seconds.

2.      27 G= Generator U/V                                                     =90 % Alarm &80 % Trip within2  seconds, Also Trip command comes from AVR(Automatic Voltage Regulator.

3.      81 U= Generator U/F                                                     =47.5 Hz for3 seconds in case of50 Hz system.

4.      81 O= Generator O/F                                                     =47.5 Hz for3 seconds in case of50 Hz system.

5.      32P= Generator Reverse Active Power                         =5 % of Sn.( Sn Total Active Power of Alternator)

6.      32Q= Generator Reverse Reactive Power                    =5 % of Sn.( Sn Total Reactive Power of Alternator)

7.      37 Low forword Power                                                   =5 % of Sn with Trip Solinoid Contact

8.       PT Fuse Failure

9.       SV, TCP = Trip Solenoid contact

10.  51 V= Voltage Controlled O/C Relay wit PT Fuse Failure

11.  50= Generator Instantaneous O/C                                  =1.3 Times.

12.  49 = Generator Over Load

13.  40G= Loss of Field

14.  46= Negative Phase Sequence                                      =15 % of FLC

15.  24=Generator Over fluxing( V/F Say110/50=2.2)           =2.3 Alarm &2.4 Trip

16.  78=Generator Pole Slipping                                            = Egen not=to Egrid, Generator Load angle more than90 degree.

17.    Generator Winding Temperature Very High                   =130 Degree Celsius

18.   Excitation Trip                   

19.  86T= Turbine Lockout Relay

In all the cases86 G will operate & Generator Breaker will Trip as well as AVR, Class B & C trip,In some cases Turbine will run( If Turbine Auxiliary is running from Stanby source)  till Generator fault rectified( in case of minor fault),After fault rectification AVR voltage buildup done& then Generator re-synchronized .In case of major fault in Generator, Turbine tripping done manually till Generator fault rectifies.

86 T (Turbine Lockout relay):-

1.      87= Generator Differential Trip                                        =5% of FLC with max200 miliseconds delay or less.

2.      51N = Directional Earth Fault                                          =5 % of FLC

3.      64N= Restricted E/F ,Neutral Displacement                   

4.      64R= Rotor E/F2nd Stage                                               =50-80 K OHM alarm &5 K OHM Trip

5.       TCP,FLD= Control Oil Pressure Low                             =8 Kg/Cm.Square in case of25Kg/Cm square System

6.       Turbine Over Speed                                                       =107-108 % of Rated Speed

7.       TCP,FLD= Lube Oil Pressure Low                                 =1.2 Kg/Cm.Square in case of2.1Kg/Cm square System.

8.       Turbine Bearing Temperature Very high                        =110 Degree C

9.       Genarator Bearing Temperature Very high                    =115 Degree C

10.   Exhaust Steam pressure very high                                 =  -0.6 Kg/Cm Squqre

11.   Exhaust Steam Temperature Very High                         =105-120 Degree C

12.   Turbine Axial Displacement very high                             =14 mills/0.40 mm

13.   Turbine Differential Expansion very high                        =2.75 mm

14.   Turbine Roror Fore Bearing X & Y Axis                          =4.5 mills/pp

15.   Turbine Roror After Bearing X & Y Axis                          =4.5 mills/pp

16.   Alternator DE bearing X & Y axis                                    =4.5 mills/pp

17.   Alternator NDE bearing X & Y axis                                 =4.5 mills/pp

18.   Hotwell Level High High                                                  =90 %

19.   Hotwell level Low Low                                                     =5 % CEP will trip

20.   Inlet Steam Pressure Low Low                                        =70 KG/cm Square at85 KG/Cm square system

21.   Inlet Steam Pressure High High                                      =91 KG/ cm square at85 KG/Cm square

22.   Inlet Steam Temperature Low Low                                  =450 degree C at510 Degree C

23.   Inlet Steam Temperature High High                                 =530 degree C at510 Degree C

In all those cases86 T will operate & Turbine Will trip. Class A or Unit Shutdown

Main difference is that in case of86T operate,86 G will definitely Trip, But in case of86 G trip not necessary86 T will trip.

Anti pumping relaying is done primarily to indicate the spring failure of TNC switch and a person need to attend the problem. The function of this relay is to cut off the supply to52C (CB closing coil) in case of TNC switch spring failure and prevent CB hunting effect (i.e. continuous closing, opening operation).

Anti pumping is also called trip free mechanism of any circuit breaker. Suppose the breaker has been instructed to close by manual instruction by pressing the TNC (trip neutral close push button) switch. The operating mechanism will start operating for closing operation.

Meanwhile a fault has taken place and relay closes the trip circuit of breaker. The trip free mechanism/ Anti pumping feature permits the circuit breaker to be tripped by protective relay even if it is under process of closing. Thus auxiliary relay (or sometimes the inbuilt feature of circuit breaker) which prevent alternate tripping and closing of the circuit breaker if closing push button is held close during fault is called the trip free mechanism or anti pumping mechanism.

Lockout Relay:

When a ‘‘drive-to-lockout’’ input is energized, the reclosing relay will go into lockout from any point in the sequence. The relay will stay in lockout until the input is removed and the breaker is closed manually or by supervisory control. Upon removal, the recloser will go through its reset sequence and return to ‘‘ready’ state.

All the different trip signals from fault detection devices are wired to the lockout relay, which is the master trip relay for the circuit breaker. It is usually a manually reset relay with an indicating flag or lamp. In case of DG a similar philosophy of tripping is used in the engine control panel in which all the mechanical failure signals are received at the engine lockout relay (86-T, T for turbine). This lockout relay also trips the generator circuit breaker.

When either the86-G or the86-T relay sends its signal to the circuit-breaker trip coil, time is taken before the circuit breaker begins to move and finally reach its fully open state. The generator switchgear is recommended to have two separate lockout relays. One will receive all the electrical protection relay trip signals, and denoted as86–1. The other will receive a master trip signal (or several trip signals) from the turbine unit control panel, and denoted as86–2.

It operates whenever any of the protection relay operates and would prevent any circuit breaker operation until the lock out relay is manually rest.

The anti-pumping relay is a device in circuit-breaker whose function is to prevent multiple breaker closures. For instance, if the operator gives the closing command to the breaker by pressing the close button and the breaker closes.However, a fault in the system causes the breaker to trip. Since the close command is still in the pressed condition, there is a chance of the breaker closing again and being tripped by the relay multiple times. This can damage the closing mechanism of the breaker.