turbine load rejection n300-16

5/20/2014 Turbine load rejection N300-16.7/537/537 Study | Science and Technology

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Turbine load rejection N300-

16.7/537/537 Study

sd / December 5, 2013

Abstract: China Resources Power Hunan Liyujiang Limited Unit 2 (300 MW) using the

conventional method of load rejection test, and for the suppression overspeed protection

control (OPC) of the frequent movement and preventing secondary soaring speed issues

, proposes to optimize digital electro-hydraulic control system (DEH) in logic and OPC

operation as soon as possible after the load rejection reheat steam pressure reducing

insights for large load rejection test reference and learn from.

words: steam turbine; digital electro-hydraulic control system; overspeed protection

control device; 300 MW unit; load rejection; speed; quadratic soaring

Abstract: The load rejecting test with conventional method on Unit 2 (300 MW) of China

Resources Power Hunan Liyujiang Co., Ltd. is described. To restrain the frequent action

of over speed protection control (OPC) and to prevent secondary acceleration over

speed, it is suggested that OPC acting logic in digital electronichydraulic system (DEH)

should be optimized and the reheat steam pressure be lowered as soon as possible

after load rejection, thus providing reference for load rejecting test on large units.

Key words: steam turbine; DEH; OPC; 300 MW unit; load rejection; rotational speed;

secondary acceleration overspeed

Hunan, China Resources Power Liyujiang Turbine Co., the No. 2 Department of Harbin

Steam Turbine Co., Ltd. introduced the U.S. Westinghouse technology to produce

N300-16.7 / 537/537 type subcritical, single reheat, twin dual exhaust, uniaxial,

condensing steam turbine. Original State Power Corporation September 28, 2000

release of power to prevent major accidents Twenty-five key requirements in the

Prevention and shaft turbine overspeed fault accident clause provides for the

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assessment of digital electro-hydraulic control system (DEH ) rocketing speed after load

shedding suppression function on technical solutions, testing instruments, meters,

DEH, the unit body and auxiliary equipment, ancillary equipment made full preparation,

on 27 August 2003 and 28 am, at the Unit 2 (300 MW) implemented a routine method

validation load rejection test, and achieved success.

load rejection test by a conventional method, to find out the Carp River Power Plant Unit

2 control system dynamic performance tests on the equipment throughout the plant load

rejection condition adaptability trials to achieve the desired purpose.

1 unit Introduction

China Resources Power Hunan Liyujiang Limited Unit 2 turbine DEH Control

Engineering from the Harbin Turbine Company Limited, using the Beijing Symphony

Bailey distributed control system to achieve.

design crew hanging gates, the high-pressure bypass can not be put into, in Bypass

Off state. Medium pressure regulating valve IV work is to take two valve approach, that

is, it does not participate in the regulation of unit speed or load. Thus, after the load

rejection, the pressure regulating valve opening IV inevitably lead unit speed soaring

again, there is the danger of speeding.

DEHs OPC (overspeed protection control) function actually contains two aspects: load

drop anticipator LDA; fly speed increased 103% of rated speed, overspeed protection

action. And the net does not make electrical or mechanical overspeed test the speed of

more than 3 090 r / min, OPC trigger until the speed is lower than 3 090 r / min reset;

generator main switch off instantly, and if the pressure cylinder exhaust steam pressure

(IEP ) Rating 15%, or greater than the measuring point fails, regardless of the rotational

speed at this time does not exceed 3 090 r / min, OPC operation of the solenoid valve to

be, the preset duration of 2 s. The two OPC function is actually complementary.

after the load rejection, DEH will automatically be forced to Operator Auto mode, the

speed, target and Setpoint are 3 000r/min.

2 pre-test preparation and improvement

2.1OPC

Given OPC simulation test load rejection characteristics essential stationary simulated

LDA trial, access to the main switch off open instantly to steam doors start closing time

delay, and close to empty the load position and a fully closed time and other

parameters; steam engine idling, when they actually tested the OPC at rated speed

103% when the loop action value and the valve closed time to confirm quickly and

reliably.

2.2LDA duration of action after the original design

LDA action, duration of 2 s. LDA action after the preset delay fundamental purpose is to

ensure that when LDA reset, the speed is still 3 090 r / min or more, the OPC 103% of

the set value circuit continues to operate. Fearing time is short, the time to delay 5 s.

2.3103% of the set value of the reset circuit is activated at speeds below the speed

if 3 090 r / min immediately reset, because the pressure regulator valve on the hydraulic

system limitations IV fixed-rate open faster, and The medium-pressure regulating valve

flow area is large, easy to cause the rotor to fly again rose to a higher speed. To this



end, the 103% value of the reset circuit is activated speed to 3 000 r / min.

2.4 to reheat steam pressure treatment

pressure bypass due after the load rejection can not be opened, cold reheat steam,

high-temperature reheat steam pipe must rely on a huge volume of steam in the

pressure regulator valve repeated IV Opening and low pressure bypass vent out. Load

shedding, it can quickly reheat steam pressure drops to a lower level is the key to

controlling the number of OPC operation. To this end, the development of the measures:

Considering the low pressure bypass pipeline longer and domestic 200 MW unit bypass

system had many incidents of strong vibrations and even blasting accidents, pre-open

low pressure bypass 5% for heating pipe;

load shedding, confirm reheat piping trap interlock open; immediately manually open low

pressure bypass to 40% to 50%, and then depending on the capacity of the bypass

itself and pipes situation quickly fully open; boiler reheater open-air assist relief valve

discharge, but must be closed before the pressure drops 0.3 MPa.

3 50% load rejection test results and analysis

rejection 50% load 100% load rejection test is a preliminary test by 50% load rejection

test, assessment of the OPC operating characteristics, LDA movement duration, high

pressure regulating valve (GV, IV) and the operating characteristics of the transient

process and characteristics rocketing speed. 50% load rejection and speed of operation

of the relationship between OPC shown in Figure 1.

right DEH control system, the first after the load rejection to prevent rocketing speed

function is achieved via OPC. Thus, from the moment the main switch tripping close to

the regulator valve to empty the load position determines the time interval of the first

rotor fly appreciation, requiring the sooner the better. The first rotor soaring extremum

3.064 r / min, the speed of 3 000r/min before load rejection of 2.13%, far less than the

industry standard DL/T711-1999 and experts recommend 5% of the required value, and

verify the OPC (LDA and 103% value) loop speed and reliability, can be 100% load

rejection test. 50% rejection of the second fly-load test appreciation 3 123 r / min higher,

but also shows the LDA operation delay of 5.0 s after the preset time (measured as

4.811 s) for rejection 50% load condition is not appropriate , it is recommended DEH no

quick closing valve (fast valving) functions under the premise of the release of the LDA

logical conditions to until the speed is lower than 3 000 r / min, the logic 100% load

rejection is also very effective.

4 100% load rejection test

4.1 rocketing speed transient process and analyze

load rejection before Turbine Speed 3 005 r / min, the generator main switch is turned

off, after 0.027 s delay , rotor speed began soaring, 2.573 s after rocketing speed up to

the first extreme 3 145 r / min.

, due to valve has been closed, the rotor begins to -0.489 5rad/s2 average angular

acceleration decreased by 32.303 s later reduced to 2 994 r / min. At this moment

before 0.937 s, OPC solenoid valves release, 0.653 s after the pressure regulator valve

starts to open IV, with IVs turn, speed up the secondary to continue soaring.



fly to second by 3.600 s Extreme 3 106 r / min, the average angular acceleration

3258rad/s2. Before the second extremum reached 1.067 s, because speed has

exceeded 3 090 r / min, OPC 103% setting circuit is activated, the valve closed loop

delay and it takes time (IV1 off time 0.12 s, IV2 off time 0.12 s ) and after the rotor

inertia up speed. continue rose 3 106 r / min.

reach extreme 3 106 r / min after 20.571 s, speed to low 2 995 r / min, the average

angular acceleration -0.565 1rad/s2. Because speed is lower than 3 000 r / min, at this

extreme point before 1.693 s, OPC 103% setting circuit release, 1.213s after the

pressure regulator valve IV1 starts to open, 1.240 s after the pressure regulator valve

begins to open IV2 , speed soaring again. 9.266 s up to third after the extreme 3 090 r /

min, the average angular acceleration 1.074rad/s2. In this extreme point before 0.360 s,

OPC103% setpoint loop due speed exceeds 3 090 r / min re-action, IV valve is closed,

IV1 off time 0.12 s, IV2 off time 0.094 s, the speed dropped.

16.967 s, the speed is reduced to 2 993 r / min, the average angular acceleration

-0.5987rad/s2. With the former principle, this extreme point reached before 1.214 s,

OPC1Z reset after 0.454 s IV1 starts to open, 0.520 s IV2 starts to open, but this time

by 85.325 s reheat steam boiler reheater time-to-air and low-pressure exhaust valve

Bypass release, has been reduced to a relatively low pressure level, the pressure

regulating valve is fully open, sufficient to fly the rotor speed increased to 3 090 r / min.

8.879 s after flying rose to a high point in the last extreme 3 007 r / min, 15.331 s after

the speed dropped to a low of 2 987 r / min. In the high-pressure regulator valve by DEH

instruction under the control of the speed stabilized at 2 993 r / min. 100% load rejection

transient reheated steam pressure shown in Figure 2, OPC, and the operation speed of

the relationship shown in Figure 3.

4.2 100% load rejection test results

eigenvalues eigenvalues calculated as follows:

a) dynamic speed overshoot = 4.66 %;

b) rotor angular acceleration r = 31.04rad / s;

c) the rotor time constant Tr = 10.13 s;

d) Rotor inertia J = 30 702.25 kg m2;

e) time constant steam volume Tv = 0.280 s.

4.3 100% load rejection Summary

generator main switch off after 5002, DEH OPC load anticipator circuit LDA action,

0.094 s after, OPC solenoid valve action, high pressure, medium pressure regulating

valve followed immediately quickly closed off time is less than 0.24 s.

100% load rejection after OPC and DEH joint action, to be effective in suppressing the

rotor speed soaring 4.66% (3 145r/min), less than the critical speed breaker Flyweight

action, and then stabilized at synchronous speed 2 994 r / min. By accurately

measuring the speed transient curve accurately obtain the time constant of the rotor

moment of inertia and other parameters.

LDA action 5.0 s after a preset delay time (measured as 4.811 s), its purpose is reset

when the LDA to ensure the speed is still 3 090 r / min or more, the OPC 103% setting



circuit continues to operate . Verified by experiment, 5 s delay time is appropriate. If

there is no valve DEH fast off function under the premise of the release of the LDA

logical conditions to until the speed is lower than 3 000 r / min, can achieve the same

purpose.

soaring in speed transient process, OPC common trigger three times, the first of which

is the LDA Since 5002 the main switch off while the pressure cylinder exhaust steam

pressure (IEP) is greater than 15% and 103% of rated joint action by To the other two by

the speed setpoint of 103% due to the role of the loop. From the domestic load rejection

test carried experience and information point of view, for the introduction of Harbin

Steam Turbine Plant Westinghouse technology to produce 300 MW units, because the

pressure regulating valve IV does not participate in speed adjustable to two valves

manner, in a 100% load rejection when, OPC 103% setpoint loop action only twice at 3

000r/min unit speed stability has not been reported. Accordingly, the second load

rejection test is successful, technically advanced. Jiaxing Power Plant Unit 2 is the

introduction of Shanghai Turbine Works Westinghouse technology to produce 300 MW

units, 50% of load rejection OPC operation 9 times 100% load rejection OPC operation

four times; Weihe Power Plant Unit 6 is produced by Harbin Turbine Works Imported

Type 300 MW units, 50% load rejection when the action four times, 100% load rejection

when the action five times; Waigaoqiao Power Plant Unit 3 is the introduction of

Shanghai Turbine plant of 300 MW Unit, 50% load rejection action six times , 100%

load rejection action 10 times; Songyu Power Plant Unit 2 (300 MW), 100% load

rejection action 13 times; Yiyang Power Plant Unit 1 Introduced (300 MW) accidental

load rejection, because there is no bypass design, OPC action 29 times.

5 Conclusions and recommendations

through the successful completion of Liyujiang Power Plant Unit 2 300 MW units 50%

and 100% load rejection test routine method to achieve the intended purpose test. The

results showed that:

a) Harbin Steam Turbine Plant type N300-16.7/537/537 subcritical, single reheat, twin

dual exhaust, uniaxial, condensing steam turbine with Control Engineering Co., Ltd.,

Harbin DEH overall design installed to meet the requirements of load shedding, the

dynamic characteristics of a good; various auxiliary and ancillary mechanical load

rejection condition for good adaptability.

b) LDA reset delay time of 2 ~ 3 s logic design, electrical power from the generator and

turbine mechanical power imbalance quick closing (fast valving) function, for after the

load rejection and target speed setpoint values were designed as 3 000 r / min for D EH,

whose role is reset when the LDA to ensure that speed is still 3 090 r / min or more, the

OPC 103% setting circuit continues to operate. Validated, 5 s delay time is appropriate,

but for the case of low load rejection was inappropriate, likely to cause secondary

soaring high speed. If there is no valve DEH fast off function under the premise of the

release of the LDA logical conditions to until the speed is lower than 3 000 r / min, can

achieve the same purpose. LDA action 5.0 s after the preset delay time (measured as 4.

811 s).

c) load rejection test conducted from the domestic experience and information point of



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Phenol-formaldehyde condensation and adsorption and treatment of phenolic

wastewater

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Shajiao A 300 MW unit of peaking sliding

pressure operation of Economic Analysis

view, the introduction of Harbin Steam Turbine Plant Westinghouse technology to

produce imported type 300 MW units, because the pressure regulating valve IV does not

participate in speed adjustable to two way valve work, in a 100% load rejection when,

OPC 103% setting circuit only twice action unit speed and stability as 3 000 r / min has

not been reported. Accordingly, the second load rejection test is successful, technically

advanced.

d) Westinghouse steam turbine original design without bypass and reheat steam

pressure after the load rejection can not be released. DEH design pressure regulator

valve IV is to take two valve way of working, to reheat piping to vent the pressure, in

order to achieve a constant speed again, the purpose of synchronous speed, which is

two valve was originally designed . While the domestic introduction of universal design

type units bypass system, in this case, DEH should be designed to IV in speed and

part of the power control and well coordinated with the bypass system, which is the

elimination of post-OPC frequent load shedding actions a fundamental way.

e) Accordingly, Westinghouse introduced the first steam turbine overspeed protection

control system of 103% OPC in speeding instantaneous shut down the regulator valve

design, the design for other units in all cases to prevent excessive speed, especially

soaring is a very effective secondary soaring in China has been widely respected and

applied.

f) For the DEH hanging barrier pressure bypass not involved in the regulation of the

domestic imported type 300 MW units, so as soon as possible after the load rejection

reheat steam pressure reduction, inhibition of OPC is an effective means of frequent

movement.

December 5, 2013 in Science and Technology.

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