ML20211E269

Protective Sys

ML20211E269
Person / Time
Site:	Seabrook
Issue date:	06/11/1986
From:	GENERAL ELECTRIC CO.
To:
Shared Package
ML20211E267	List: ML20211E255 ML20211E269 ML20211E284 ML20211E290
References
GEK-46487A, NUDOCS 8606130298
Download: ML20211E269 (4)

Text

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INSTRUCTISNS OEx-4emA d/.2 066

, PROTECTIVE SYSTEM l

GENERAL of devices, all components of the Mechanical-Hy-draulic Trip System

'itepurposecf the Protective Systemis to detect undestrahle or dangerous operating conditions of the turbine-generator, tag apprtspriate trip actions, a. Mechanical Shut-Off Velve (MSOV) and p ovide information *o the operator about the t detected conditions and the consequent actions. In b. Mechanical Trip Valve (MTV) addition, mecns are provided for lestingall testable equipment and circutts. c. Mecharical I4ckout Solenoid Vahe (MLV) l I

The Protective System consists of two major d. Dectrical Mp van m) subsy stems;

e. Electrical Lockout Solenoid Valve (ELV) 1 %e Mecharical-Ifydraulic Trip System -

described in detail in the Wrbine Section of no MSOV and MTV arecontrolled hydenlically the Instruct 19n Book, by the Mechacical Trip Pilot Valve (MTPV), and when their pilot iltes are depresst rized, these l 2. De Electrical Trip and Monitoring System valves shut off their irput lir.e and drata their out-l (T&M) - described in detail in the Electro- put line, tripping the ETS.

! hydraulic Secticn of the Instructico Dook.

De MLV is controlled electrically by the TLM.

'C_ nis instruction describes in summary both sub- andwhen energized, itbypasses the MSOV and MTV, i

systems and their relationships, permitting these two valves and two of the three signal paths that actuate them to be tested without A simplified signal flow diagram of the Protec- tripping the ETS.

tive System is shown in l'igure 1.

'Ihe ETV ls cortrolled hydraulicallyby the Elec-trical Trip Solencid Valve (ETSV), and when its pilot PRINCIPLE OF OPERATION line is depressurized, this valve shi.ta off its input line and drains its output line, trippirg the ETS, ne Emergene? Trip System (ETS) is the high-pressure fluid system that, when in the Heset or De ELV is controlled electrically by the T&M, pressurized state, permits all ofeamvalves to open and, when energized, bypasses the ETV permitting in the presence of opening signals from the EHC. this valve and the signal path that actuates it to be When in the tripped or depressurized state, it over- tested without tripping the ETS.

ridesallopeningsignals, and trips the Main and He-heatStop Valves, the Control Valves, and the Inter. In order to trip the ETS, any tripping signalhas C cept Valves directly by way of their disc-dump to actuate or.e or both of the MTPV or the ETSV.

s ulves, and trips the Extraction Check Valves Each of these two caseswill be examined separately, thn. ugh the Air Relay Dump Valve. %e principal outputfuncitonof the Protective Systemis to control the state of the ETS. 1, MTPV ACTUATION nis valve is operated mechanically by the I. MECHANICAL-IIYDRAULIC TRIP SYSTEM Trip Latch Hod, which is tripped (i.e., (1-lowed to move under the influence of a charged

%e ETS is pressurized from the high-pressure spring to a position where the M TPV is tripped) l hydraulle flufd supply, through the following chain by the Trip l'inger.

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PROTECTIVE SYSTEM, GEK-46487A The Trip Finger is operated by: which are connected to the T&M and provide infor-mation about the state of the various components

a. The Mechanical Overspeed Trip Device (valves, piston, Trip Latch Rod, MTH, etc.).

(OST)

This is actuated *duringan overspeedof the H. ELECTRICAL TRIP AND MONITORING SYS-turbine exceeding the OST setting, or at TEM (T&M) rated speedduring aMcchanicalOverspeed TripTest. During thistest the T&M ener- The principal function of this part of the Protec-gizes the Oil Trip Solenoid Valve (OTSV) tive System is to connect all external trip signals which admits lubrication oil to the OST (except the trippingsignals from the OST and MTH, f causing it to trip. A coordinated actuation which actdirectly onthe Mechanical-Hydraulic Trip i of the MLV preventsthe ETS from tripping. System) to one or both of the MTSV and ETSV after suitah!e modifications by logic circuits. Each of

b. The Mechanical Trip Piston (MTP) these valvesis independentlycapable of tripping the ETS.

This is he'd in the reset position by tur-bine lube oil pressure. The piston is al- The incoming trip signals are arrant;ed into two lowed to trip by actionof a springwhen the groups:

oil pressure is lost or when the oil is shut off by the Mechanical Trip Solenoid Valve 1. Signals I:xternal to the EHC Cabinet:

(MTSV) . This valve is energized by the T&M during a 125V trip as it will be de- These cause 125V Trips;i.e., they activate fined later, or during a MTP Test. In the the 125V Trip Bus and energize the MTSV latter case a coordinated actuation of the directly.

MLV prevents the ETS from tripping,

c. The Manual Trip Handle (MTH) In addition, the 24V trip circuit is indirectly operated through a set of relays (crosstrip),

There is no provision for testing the MTH and the 125V Trip Bus is locked up after a

(- under lockout conditions. An MTH test short time delay, will result in an actual trip.

When the generator circuit breaker is open, The Trip Latch Rod, once tripped, latches and the MTV and ETS are tripped, an addi-mechanically, and remains in the tripped posi- tional lock-up circuit is established through tion even after the condition that caused it to pressure switch contacts, trip (a, b, or c) hasbeen cleared. It is reset by the Reset Mechanism, consisting of: During a MTP Test the MTSV is energized without activating the 125V Trip Bus, the cross

a. De Oil Reset Solenoid Valve (ORSV) - trip circuit and the lock-up circuits, when energized by the T&M actuates the Oil Reset Piston. 2. Signals internal to the EHC Cabinet:

b. The Oil Reset Piston (ORP) - resets the These cause a 24V trip, i.e., they de-ener-Trip Latch Rod and the MTPV, which in gize the ETSV solenoids througha set of re-turn resets the MSOV and MTV. layscor. tacts, and lock-up the 24V tripcircuit through another set of relays contacts.

2. ETSV ACTUATION The first set of relays is also operatedduring a Trip Anticipator action (if applicable) or dur-His valvehastwo 24 VDC solenoidswhichare ing an Electrical Trip Test;in these two cases normally energized when the ETSV is in the thelock-up circuitis notactivatedand the sit-reset state. The valve trips when both sole- uation is cleared once the cause producing it nolds are de-energized. Pallure of one sole- is removed, without necessitatingany positive noid willnot cause aspurioustrip. The sole- resetting action, noids are connected to the T&M and are de-energized during a 24V trip as willbe defined Of the signalsinternal tothe EHC Cabinet, the later, duringa Trip Anticipator action (if ap- Loss of Both $eed Signal and the Back-Up plicable), or during an Electrical Trip Test. Overspeed Trip Signalenergize, in addition to In the latter case, a co-ordinatedactuation of the trippingand the lockingrelays, a third set

(.~ the ELY prevents the ETS from tripping. of relays whicheross trip the 125V Trip Bus.

The other three signals that cause a 24V trip The Mechanical-Hydraulic Trip System includes a do not energize these cross trip relays; how-number of pressure switches and limit switches ever of these, the Master Trip Button causes 3

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GEK-46487A, PROTECTIVE SYFTEM q

a 125V Trip thr0cgha separate contract, The The T4M also cor.tains the Icgic for testing the /

Customer, at his option, can do the same for trip devices. (Mechanical Overtpced, Mechanical Customer Trips energizedbythe 125V Station Trip Pisten and Electrical Triptests.) When one of Battery. On_ ly the lcss o( 125 VDC when speed these tests is initiated, the TLM logic provides a is below 75% of rated inevitably produces a soquence of signalsto the appropria*elockout, trip, 24V Trip alone. and reset valve solenoids and receives feedback signals that allow it to sense the status of the Me-A loss of 24 VDC de-encrgizes the ETSV chanical-Hydraulic Trip System aftereach step and solenoids, causing a 24V Trip andeross trips whether the test was successful.

the 125V Trip B us.

In summary, all trip signals to the tam, ex- Each of the fhree Back-Up Overspeed Trip Cir-

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cept the loss of 125 VDC, and - if the customer so cults can be separately tested without causing an chooses - the customer trips operated with station actual trip. These circuits, as well as many other battery, activate two independent paths throughout trip circuits of the T&M, are arranged in a two-the T&M and the Mechanical-Hydraulic Trip Sys- out-of-three Icgic system.

tem, and redundantly trip ine ETS.

When the condition that caused atrip has cleared, The Thrust Bearing Wear Detector is tested via the Elic can be reset bydepressingthe Reset Button an automatic system from the contrei panel, on the Turbine panel. This will:

Finally, the T&M System contains logic for the

a. Dreak the lock-up circuits, display of the status of the ETS, Mechanical-Hy-

b. Reset the MTV throughthe Reset Mechanism, draulic System, and T&M itself, logic for annun-clation and First Hit Detection of tripping and other The Reset button must be held down until the "RE- abnormalconditions, and provides switchingsignals SET" lightcomes on toasaare the ETS pressure has for control functions to other sections of the EllC been re-established, and for customer use. .

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10-76 (1M)

GENER AL $ ELECTRIC T