CN100349347C - Large-scale steamer generator neutral point lead-out mode and arrangement protecting method - Google Patents

Abstract

The present invention relates to a neutral point leading out mode for a large steam turbine generator and a device protecting method, which belongs to the field of the design and the manufacture of alternating current machines. On the premise of not changing the number of leading-out terminals at the neutral point side of the steam turbine generator, the present invention independently leads out the second branches (or the first branches) of an A and a B phases, respectively installs branches TA, then connects A1, B1, C1 and C2 branches (or A2, B2, C1 and C2 branches) together for forming a third leading-out terminal at the neutral point side, and installs TA. Through the TA of the A and B phases, traditional incomplete longitudinal difference protection can be formed. A novel differential protection scheme is formed from the TA of the C phases. Through the comprehensive simulation calculation of the internal faults of two 300MW steam turbine generators and the check of the sensitivity of the protection scheme, the properties of the present invention are obviously better than the traditional arrangement of neutral point leading out modes and protection schemes for generators. Furthermore, the present invention does not need the increase of any hardware investment and is approved by electrical machine manufacturing factories.

Description

Large turbo-type generator drawing-off way from neutral point and protection collocation method

Technical field

The invention belongs to the technical field of relay protection with power system main equipment of manufacturing and designing of alternating current machine, relate in particular to large turbo-type generator drawing-off way from neutral point and protection configuration.

Background technology

The large turbo-type generator stator winding fault is the very strong fault of motor common damage.Very big short circuit current can produce destructive serious electromagnetic force during internal fault, and it is overheated also may to produce, and burns winding and iron core.The negative phase-sequence magnetic field that fault produces may substantially exceed the design permissible value, causes the major injury of rotor.Therefore, China's Protection Technology rules stipulate that clearly large turbo-type generator need install the alternate and interturn short circuit protection of stator winding.

But the most neutral point side of existing turbo generator are only drawn 3 terminals (referring to Fig. 1), can only install complete longitudinal difference protection, and this protection only can be reacted the phase fault of Stator Coil, can not move to turn-to-turn short circuit.

Result of study shows in the turbo generator neutral point side draws 4 or 6 outlet terminals and installs the branch current instrument transformer (referring to Fig. 2 and Fig. 3; current transformer is represented with TA), the main protection configuration scheme that adopts zero-sequence current type transverse differential protection+incomplete differential protection or split phase transverse differential protection+incomplete differential protection will improve the performance of protection scheme greatly.

But, for the generator designs manufacturing,, all on outlet structure, do great change (referring to Fig. 4) even only increase by 1 leading-out terminal.Have following several scheme available through the design of electrical motor man analysis: the one, the irdome that extends out, the 2nd, widen and irdome; The 3rd, above support, increase by one and go out irdome.But scheme one is subjected to the restriction that motor overall dimension and 300MW and above turbo generator must adopt TPY type TA (about external diameter 1000mm); Scheme two certainly will reduce the support stiffness of end cap bearing, will make critical whirling speed reduce and reduce stability; Scheme three is subjected to the turbo generator type of cooling---the restriction of Backpack type cooler commonly used.In addition, above-mentioned measure all will influence transportation (its transportation clearance reaches capacity), the machine hole of generator unit and a lot of aspects such as design of factory building, and it is very big to make that Fig. 2 and technological transformation shown in Figure 3 implement difficulty.

As seen, in order to overcome the defective of above-mentioned two kinds of schemes, must new drawing-off way from neutral point and the protection collocation method of research.

Summary of the invention

The object of the present invention is to provide novel drawing-off way from neutral point of a kind of large turbo-type generator and protection collocation method.

In order to guarantee the safe operation of large turbo-type generator, the present invention proposes novel drawing-off way from neutral point of large turbo-type generator and protection collocation method.Its principle is: under the prerequisite that does not change turbo generator neutral point side exit subnumber (to reduce the difficulty that design of electrical motor is made), by reasonable change generator each mutually the compound mode of each branch's lead-in wire line rod to form new neutral point side leading-out terminal.May further comprise the steps (referring to Fig. 5):

(1) the 2nd branch (or the 1st branch) of turbo generator A, B phase is drawn separately forming the 1st and the 2nd leading-out terminal of neutral point side, and on the 1st and the 2nd leading-out terminal, install branch current instrument transformer TA1 and TA2;

(2) A1, B1, C1 and C2 branch (or A2, B2, C1 and C2 branch) are connected together with the 3rd leading-out terminal of formation neutral point side, and on the 3rd leading-out terminal, install current transformer TA3;

(3) constitute traditional incomplete differential protection by the current transformer TA4 of A camera end and the current transformer TA1 of neutral point side;

(4) constitute traditional incomplete differential protection by the current transformer TA5 of B camera end and the current transformer TA2 of neutral point side;

(5) constitute a kind of differential protection scheme by the current transformer TA6 of C camera end and the current transformer TA3 of neutral point side, the adjusting of its operating characteristics with traditional incomplete differential protection.

Experimental results show that: the phase fault that the small turn number that the end fault type that above-mentioned three kinds of protection schemes can not action message can comprise the C phase falls far short with the short dot of turn-to-turn short circuit of identical branch and short circuit branch with the big number of turn of the turn-to-turn short circuit of identical branch, C phase; Simultaneously, reduced the difficulty that design of electrical motor is made again.

Description of drawings

Fig. 1 is turbo generator among the present invention traditional outlet method and protection allocation plan.

Fig. 2 draws 4 terminals and installs horizontal difference of zero-sequence current type and incomplete differential protection allocation plan for turbo generator neutral point side among the present invention.

Fig. 3 draws 6 terminals for turbo generator neutral point side among the present invention and mutually horizontal difference and incomplete differential protection allocation plan are split in installing.

Fig. 4 is the medium-and-large-sized turbo generator overall dimension of a present invention schematic diagram.

Fig. 5 is novel drawing-off way from neutral point of the medium-and-large-sized turbo generator of the present invention and protection allocation plan.

Fig. 6 for novel main protection scheme among the present invention can not action message the fault type schematic diagram.

Fig. 7 for the big first number of turn among the present invention with identical branch turn-to-turn short circuit schematic diagram.

Embodiment

In order to verify the performance of above-mentioned novel drawing-off way from neutral point and protection scheme; be example with two 300MW turbo generators (number of stator slots is respectively 54 grooves and 60 grooves) below; utilization " multi-loop analysis method " has been carried out analytical calculation to its sensitivity on the basis of comprehensive internal fault simulation calculation.

Same groove and end fault that two 300MW turbo generators of table 1 actual capabilities take place

Turbo generator	The internal fault number		Turn-to-turn short circuit		Phase fault
						With identical branch	The different branches of homophase
			54 grooves	With the groove number of faults				54	0	24	30
The end number of faults	1077	168			30	879
				60 grooves			With the groove number of faults	60	0	24	36
The end number of faults	1317	216	30		1071

When two turbo generators of table 2 are incorporated into the power networks zero load to main protection scheme akinesia number of faults and character thereof shown in the end fault graph 5

Turbo generator	Can not the action message number of faults	Turn-to-turn short circuit									Phase fault
												With identical branch								The different branches of homophase
		1 circle	2 circles	3 circles	4 circles	5 circles	6 circles	7 circles	8 circles
										54 grooves		23	8	0	0	0	1	2	2		/	0	10
60 grooves	27	10	2	0	0	0	1	2	2		0									10

Definite foundation of internal fault shown in the table 1 is the stator winding connection layout that motor manufactory provides, and all these short circuits are not to set arbitrarily.Table 2 pair main protection scheme shown in Figure 5 can not the action message number of faults (with sensitivity K _Sen＜1.5 is the boundary; adjusting of main protection scheme operating characteristics) referring to " adjust calculate guide rule " and character carried out statistical analysis; find that its akinesia number of faults accounts for about 2% of fault sum, and main protection scheme akinesia number of faults shown in Figure 1 accounts for about 20% of fault sum.The novel drawing-off way from neutral point shown in Figure 5 and the performance of protection scheme will significantly be better than the traditional generator neutral point lead-out mode and the configuration of protection scheme, and this scheme need not increase any hardware investment, have obtained the makers' approval of motor.

By further analysis; find that phase fault that small turn number that end fault type that main protection scheme shown in Figure 5 can not action message comprises the C phase falls far short with the short dot of identical branch turn-to-turn short circuit (shown in Fig. 6 dotted arrow) and short circuit branch with the big number of turn of identical branch turn-to-turn short circuit (shown in Fig. 6 solid arrow), C phase is (shown in Fig. 6 dash-dot arrows; the short dot of A1 (or B1) branch is near neutral point side, and the short dot of C1 (or C2) branch is near the machine end).Because it is identical that dotted line and fault shown in the dash-dot arrows come down to, and is that example is analyzed with the big number of turn of C1 branch with identical branch turn-to-turn short circuit (referring to Fig. 7) below.

Fault shown in the dotted arrow is that 54 groove turbo generators are under the no-load running mode that is incorporated into the power networks among Fig. 7, the C lower floor limit of the 1st branch road Line 1 circle mutually takes place with the turn-to-turn short circuit of identical branch at the end portions cross place on the limit, upper strata of No. 9 coil of the 1st branch road mutually with C, and the short circuit number of turn is 7 circles.Size of each branch road (comprising the short circuit additional branches) fundamental current (effective value, unit are A, down together) and phase place are as follows:

Owing to be that the big number of turn is with the turn-to-turn short circuit of identical branch; air-gap field is still based on the space first-harmonic; non-fault is the size and the phase place of two branch currents (if the C1 branch head and the tail short circuit that is more or less the same mutually; two branch currents are all identical mutually for then non-fault); cause the size and the phase place of non-fault phase incomplete differential protection both sides electric current to be more or less the same; make that differential current is too little and stalling current is bigger; so the sensitivity that non-fault is protected mutually is not high, A, the B sensitivity coefficient of not exclusively vertical difference mutually are respectively 0.932,0.904.

Make a concrete analysis of the both sides electric current of the mutually novel differential protection of C below again

With

${\stackrel{.}{I}}_1={\stackrel{.}{I}}_{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="C20051001144300061.png,C20051001144300071.png"\; state="\{\{state\}\}">C</figure-callout>}1}+{\stackrel{.}{I}}_{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="C20051001144300061.png,C20051001144300071.png"\; state="\{\{state\}\}">C</figure-callout>}2},$ ${\stackrel{.}{I}}_2=2\&times;({\stackrel{.}{I}}_{\mathrm{<figure-callout\; id="1"\; label="A"\; filenames="C20051001144300061.png,C20051001144300071.png"\; state="\{\{state\}\}">A</figure-callout>}1}+{\stackrel{.}{I}}_{\mathrm{<figure-callout\; id="1"\; label="B"\; filenames="C20051001144300061.png,C20051001144300071.png"\; state="\{\{state\}\}">B</figure-callout>}1}+{\stackrel{.}{I}}_{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="C20051001144300061.png,C20051001144300071.png"\; state="\{\{state\}\}">C</figure-callout>}1}+{\stackrel{.}{I}}_{C2}),$

So ${\stackrel{.}{I}}_2-{\stackrel{.}{I}}_1=2{\stackrel{.}{I}}_{\mathrm{<figure-callout\; id="1"\; label="A"\; filenames="C20051001144300061.png,C20051001144300071.png"\; state="\{\{state\}\}">A</figure-callout>}1}+2{\stackrel{.}{I}}_{\mathrm{<figure-callout\; id="1"\; label="B"\; filenames="C20051001144300061.png,C20051001144300071.png"\; state="\{\{state\}\}">B</figure-callout>}1}+{\stackrel{.}{I}}_{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="C20051001144300061.png,C20051001144300071.png"\; state="\{\{state\}\}">C</figure-callout>}1}+{\stackrel{.}{I}}_{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="C20051001144300061.png,C20051001144300071.png"\; state="\{\{state\}\}">C</figure-callout>}2},$ Because ${\stackrel{.}{I}}_{\mathrm{<figure-callout\; id="1"\; label="A"\; filenames="C20051001144300061.png,C20051001144300071.png"\; state="\{\{state\}\}">A</figure-callout>}1}\&ap;{\stackrel{.}{I}}_{\mathrm{<figure-callout\; id="2"\; label="A"\; filenames="C20051001144300061.png,C20051001144300071.png"\; state="\{\{state\}\}">A</figure-callout>}2},$ ${\stackrel{.}{I}}_{\mathrm{<figure-callout\; id="1"\; label="B"\; filenames="C20051001144300061.png,C20051001144300071.png"\; state="\{\{state\}\}">B</figure-callout>}1}\&ap;{\stackrel{.}{I}}_{\mathrm{<figure-callout\; id="2"\; label="B"\; filenames="C20051001144300061.png,C20051001144300071.png"\; state="\{\{state\}\}">B</figure-callout>}2},$

So ${\stackrel{.}{I}}_2-{\stackrel{.}{I}}_1={\stackrel{.}{I}}_{A1}+{\stackrel{.}{I}}_{A2}+{\stackrel{.}{I}}_{\mathrm{<figure-callout\; id="1"\; label="B"\; filenames="C20051001144300061.png,C20051001144300071.png"\; state="\{\{state\}\}">B</figure-callout>}1}+{\stackrel{.}{I}}_{\mathrm{<figure-callout\; id="2"\; label="B"\; filenames="C20051001144300061.png,C20051001144300071.png"\; state="\{\{state\}\}">B</figure-callout>}2}+{\stackrel{.}{I}}_{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="C20051001144300061.png,C20051001144300071.png"\; state="\{\{state\}\}">C</figure-callout>}1}+{\stackrel{.}{I}}_{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="C20051001144300061.png,C20051001144300071.png"\; state="\{\{state\}\}">C</figure-callout>}2}={\stackrel{.}{I}}_A+{\stackrel{.}{I}}_B+{\stackrel{.}{I}}_C.$

Because high-rating generator generally is considered as isolated neutral system, so according to Kirchhoff's current law (KCL), ${\stackrel{.}{I}}_A+{\stackrel{.}{I}}_B+{\stackrel{.}{I}}_C=0,$ So C phase differential protection both sides difference between currents is also very little, as mentioned above, the sensitivity coefficient of C phase differential protection is not high yet, only is 0.684.

By top qualitative analysis, recognize that fault shown in Figure 7 is the operating dead zone of novel protected scheme really, illustrates further the correctness of simulation calculation and statistical analysis.

Claims (2)

1. large turbo-type generator drawing-off way from neutral point and protection collocation method; it is characterized in that; keeping turbo generator neutral point side exit subnumber is under 3 the prerequisite; respectively the compound mode of each branch's lead-in wire line rod is to form neutral point side leading-out terminal described below mutually by changing described generator, and it contains following steps successively:

Step 1. represents the 2nd branch of turbo generator A phase, B phase respectively with A2, B2, draw separately forming the 1st and the 2nd leading-out terminal of neutral point side, and install branch current instrument transformer TA1 and TA2 on described the 1st and the 2nd leading-out terminal;

Step 2. the A that represents with A1 mutually the 1st branch, the B that represents with B1 mutually the 1st branch, the C that represents with C1, C2 respectively mutually the 1st branch and the 2nd branch be connected together forming the 3rd leading-out terminal of neutral point side, and on described the 3rd leading-out terminal, install current transformer TA3;

Step 3. is at current transformer TA4 of A camera termination, and the current transformer TA1 of it and described neutral point side constitutes traditional incomplete differential protection;

Step 4. is at current transformer TA5 of B camera termination, and the current transformer TA2 of it and described neutral point side constitutes traditional incomplete differential protection;

Step 5. is at C camera termination current transformer TA6; the current transformer TA3 of it and neutral point side constitutes a kind of differential protection; adjusting of its operating characteristics is identical with traditional incomplete differential protection; when normal operation of generator or external fault, the differential protection both sides difference between currents of C phase is very little.

2. a kind of large turbo-type generator drawing-off way from neutral point according to claim 1 and protection collocation method is characterized in that:

A phase in the described step 1, the 2nd branch of B phase replace with the 1st branch of A phase, B phase respectively;

A in the described step 2 the 1st branch, B phase the 1st branch mutually replaces with A phase the 2nd branch, B phase the 2nd branch respectively successively, and the 1st, the 2nd branch of C phase keeps former state.

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