CN104779582A - Method for identifying sympathetic inrush current and fault current in transformer protection - Google Patents
Method for identifying sympathetic inrush current and fault current in transformer protection Download PDFInfo
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- CN104779582A CN104779582A CN201510101914.1A CN201510101914A CN104779582A CN 104779582 A CN104779582 A CN 104779582A CN 201510101914 A CN201510101914 A CN 201510101914A CN 104779582 A CN104779582 A CN 104779582A
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Abstract
The invention discloses a method for identifying sympathetic inrush current and fault current in transformer protection, and solves a difficult problem in accurate identification of the fault current and the sympathetic inrush current of a transformer. When any one of A phase difference current, B phase difference current and C phase difference current is not lower than a difference current setting value delta I of the transformer, a difference delta S between the high-voltage-side secondary current area Sy(high voltage side) of the transformer and the medium-voltage-side secondary current area Sy(medium voltage side) of the transformer is calculated; when the area difference delta S between the high-voltage-side secondary current area Sy(high voltage side) and the medium-voltage-side secondary current area Sy(medium voltage side) is greater than a current area difference setting value of the difference between the high-voltage-side secondary current area and the medium-voltage-side secondary current area, and a difference between a fundamental wave phase angle of high-voltage-side secondary current and a fundamental wave phase angle of medium-voltage-side secondary current is not greater than 90 degrees, the current of the transformer is the external fault current or the sympathetic inrush current. The method can be used for accurately identifying the fault current and the sympathetic inrush current of the transformer, so that false operation of differential protection of the transformer is avoided and normal running of main equipment of a power grid is guaranteed.
Description
Technical field
The present invention relates to the fault current discrimination method in a kind of power system transformer relaying protection; in particular to the discrimination method of the sympathetic inrush in a kind of transformer relay protecting and fault current; accurately can be determined the fault current character of protection equipment for transformer by the method, reach the object ensureing that transformer safety is run.
Background technology
Along with high pressure long-distance transmission line Large scale construction and put into operation, the application of high-power transformer is increasing, while meeting large capacity transmission, also has higher requirement to the reliability of tranformer protection and quick-action.Differential protection is one of main protection scheme of power transformer interior fault, and differential protection mainly solves two problems: one is differentiate magnetizing inrush current and fault current; Two is distinguish internal fault and external fault.Long-term operating experience shows, transformer differential protection can distinguish internal fault and external fault to a certain extent preferably, but also there is certain problem in the discriminating of magnetizing inrush current and fault current.In recent years, in running, there is the phenomenon of a lot of air-drop transformer, caused the accident of adjacent parallel connection or cascade transformer differential protection malfunction, bring very large harm to the normal operation of main equipment.At present, also effectively do not differentiate the method for transformer fault electric current and sympathetic inrush, bring hidden danger to the safe operation of high-power transformer.
Summary of the invention
The invention provides the discrimination method of sympathetic inrush in a kind of tranformer protection and fault current, solve the difficult problem accurately differentiating transformer fault electric current and sympathetic inrush, avoid the misoperation of transformer differential protection.
The present invention solves above technical problem by the following technical programs:
Sympathetic inrush in tranformer protection and a discrimination method for fault current, comprise the following steps:
The high-pressure side secondary current sampled value of the transformer of the first step, acquisition Y-Y-Δ wiring patterns, obtains the medium voltage side secondary current sampled value of the transformer of Y-Y-Δ wiring patterns, obtains the low-pressure side secondary current sampled value of the transformer of Y-Y-Δ wiring patterns;
Second step, the high-pressure side secondary current sampled value by obtaining, medium voltage side secondary current sampled value and low-pressure side secondary current sampled value, carry out differential filtering respectively;
3rd step, by the high-pressure side secondary current sampled value after differential filtering, the medium voltage side secondary current sampled value after differential filtering and the low-pressure side secondary current sampled value after differential filtering, carry out all-wave Fourier digital filtering respectively, obtain high voltage side of transformer secondary current fundamental voltage amplitude and phase angle, transformer medium voltage side secondary current fundamental voltage amplitude and phase angle, step down side secondary current fundamental voltage amplitude and phase angle;
The computational methods of high-pressure side secondary current fundamental voltage amplitude and phase angle are:
The sampling number first setting the every cycle of high voltage side of transformer secondary current is N, then the current sampling data of high voltage side of transformer secondary current sampled point is
i(
k),
k=0,1,2 ... N-1, the sampling interval is Δ t;
According to following Fourier transform formula:
Wherein:
ωthe angular frequency of-high voltage side of transformer secondary current cycle;
After obtaining the sinusoidal coefficients of first-harmonic, then the plural form of fundametal compoment is:
High-pressure side secondary current fundamental voltage amplitude is:
High-pressure side secondary current first-harmonic phase angle is:
Utilize above same method, calculate transformer medium voltage side secondary current fundamental voltage amplitude and phase angle, and step down side secondary current fundamental voltage amplitude and phase angle;
4th step, utilize Y-Δ transform method, adjustment transformer each side current amplitude and phase angle; The high-pressure side secondary current of the Y connection of the transformer of Y-Y-Δ wiring patterns is converted to the high-pressure side secondary current of Δ connection, the medium voltage side secondary current of the Y connection of the transformer of Y-Y-Δ wiring patterns is converted to the medium voltage side secondary current of Δ connection, the low-pressure side secondary current side of the Δ connection of the transformer of Y-Y-Δ wiring patterns is constant; Transformer medium voltage side current amplitude is converted to high voltage side of transformer according to transformer voltage ratio, step down side current amplitude is converted to high voltage side of transformer according to transformer voltage ratio; Obtain after filtering and conversion thus: high-pressure side A phase secondary current
, high-pressure side B phase secondary current
, high-pressure side C phase secondary current
, medium voltage side A phase secondary current
, medium voltage side B phase secondary current
, medium voltage side C phase secondary current
, low-pressure side A phase secondary current
, low-pressure side B phase secondary current
, low-pressure side C phase secondary current
;
The spill current of the tranformer protection of the 5th step, acquisition Y-Y-Δ wiring patterns starts setting value Δ I;
6th step, calculating A phase phase spill current
, B phase phase spill current
with C phase phase spill current
, computing formula is as follows:
7th step, to obtain respectively: the A phase secondary current difference in areas setting value S of the high-pressure side A phase secondary current area of transformer and the medium voltage side A phase secondary current difference in areas of transformer
a; The B phase secondary current difference in areas setting value S of the high-pressure side B phase secondary current area of transformer and the medium voltage side B phase secondary current difference in areas of transformer
b; The C phase secondary current difference in areas setting value S of the high-pressure side C phase secondary current area of transformer and the medium voltage side C phase secondary current difference in areas of transformer
c;
8th step, when A phase phase spill current
when amplitude is more than or equal to the spill current startup setting value Δ I of tranformer protection, the high-pressure side A phase secondary current area S of calculating transformer
y high-pressure side Awith the medium voltage side A phase secondary current area S of transformer
y medium voltage side Apoor Δ S
a, high-pressure side A phase secondary current during calculating, will be adopted
, medium voltage side A phase secondary current
, low-pressure side A phase secondary current
;
High-pressure side secondary current area S
y high-pressure side Acomputational methods be:
The sampling number first setting the every cycle of high voltage side of transformer electric current is N, the current sampling data of high voltage side of transformer current sample point
i(
k),
k=0,1,2 ... N-1, the sampling interval is Δ t, and utilize rectangle (or trapezoidal) method, calculate the spacer area between two sampled points, computing formula is as follows:
Δ
S 0=
i(0)*Δ
t；
Δ
S 1=
i(1)*Δ
t；
Δ
S 2=
i(2)*Δ
t；
……；
Δ
S N-1
=
i(
N-1)*Δ
t；
The sampled point that acquisition phase spill current is more than or equal to the spill current startup setting value Δ I moment of tranformer protection is
x;
Then
ymoment high voltage side of transformer A phase secondary current area:
Medium voltage side A phase secondary current area S
y medium voltage side Acomputational methods be:
The sampling number first setting the every cycle of transformer medium voltage side electric current is N, the current sampling data of transformer medium voltage side current sample point
i(
k),
k=0,1,2 ... N-1, the sampling interval is Δ t, and utilize rectangle (or trapezoidal) method, calculate the spacer area between two sampled points, computing formula is as follows:
Δ
S 0=
i(0)*Δ
t；
Δ
S 1=
i(1)*Δ
t；
Δ
S 2=
i(2)*Δ
t；
……；
Δ
S N-1
=
i(
N-1)*Δ
t；
The sampled point that acquisition phase spill current is more than or equal to the spill current startup setting value Δ I moment of tranformer protection is
x;
Then
ymoment transformer medium voltage side A phase secondary current area:
High-pressure side A phase secondary current area S
y high-pressure side Awith medium voltage side A phase secondary current area S
y medium voltage side Adifference in areas be Δ S
a;
9th step, when A phase phase spill current
when amplitude is more than or equal to the spill current startup setting value Δ I of transformer, calculate high-pressure side A phase secondary current first-harmonic phase angle and medium voltage side A phase secondary current first-harmonic phase angle, the high-pressure side A phase secondary current after the 4th step will be adopted during calculating whole simultaneously
, medium voltage side A phase secondary current
, low-pressure side A phase secondary current
;
Tenth step, as high-pressure side A phase secondary current area S
y high-pressure side Awith medium voltage side A phase secondary current area S
y medium voltage side Adifference in areas Δ S
abe more than or equal to A phase secondary current difference in areas setting value S
a, and, when high-pressure side A phase secondary current first-harmonic phase angle is greater than 90 degree with medium voltage side A phase secondary current first-harmonic phase angle difference, be transformer troubles inside the sample space electric current; As high-pressure side A phase secondary current area S
y high-pressure side Awith medium voltage side A phase secondary current area S
y medium voltage side Adifference in areas Δ S
abe more than or equal to A phase secondary current difference in areas setting value S
a, and, when high-pressure side A phase secondary current first-harmonic phase angle is less than or equal to 90 degree with medium voltage side A phase secondary current first-harmonic phase angle difference, be transformer external area error electric current or sympathetic inrush;
11 step, when B phase phase spill current
when amplitude is more than or equal to the spill current startup setting value Δ I of tranformer protection, the high-pressure side B phase secondary current area S of calculating transformer
y high-pressure side Bwith the medium voltage side B phase secondary current area S of transformer
y medium voltage side Bpoor Δ S
b, high-pressure side B phase secondary current during calculating, will be adopted
, medium voltage side B phase secondary current
, low-pressure side B phase secondary current
;
High-pressure side B phase secondary current area S
y high-pressure side Bwith the medium voltage side B phase secondary current area S of transformer
y medium voltage side Bcomputational methods and the 8th step high-pressure side A phase secondary current area S
y high-pressure side Awith medium voltage side A phase secondary current area S
y medium voltage side Acomputational methods identical, high-pressure side B phase secondary current area S
y high-pressure side Bwith medium voltage side B phase secondary current area S
y medium voltage side Bdifference in areas be Δ S
b;
12 step, when B phase phase spill current
when amplitude is more than or equal to the spill current startup setting value Δ I of tranformer protection, calculate high-pressure side B phase secondary current first-harmonic phase angle and medium voltage side B phase secondary current first-harmonic phase angle, the high-pressure side B phase secondary current after the 4th step will be adopted during calculating whole simultaneously
, medium voltage side B phase secondary current
, low-pressure side A phase secondary current
;
13 step, as high-pressure side B phase secondary current area S
y high-pressure side Bwith medium voltage side B phase secondary current area S
y medium voltage side Bdifference in areas Δ S
bbe more than or equal to B phase secondary current difference in areas setting value S
b, and, when high-pressure side B phase secondary current first-harmonic phase angle is greater than 90 degree with medium voltage side B phase secondary current first-harmonic phase angle difference, be transformer troubles inside the sample space electric current; As high-pressure side B phase secondary current area S
y high-pressure side Bwith medium voltage side B phase secondary current area S
y medium voltage side Bdifference in areas Δ S
bbe more than or equal to B phase secondary current difference in areas setting value S
b, and, when high-pressure side B phase secondary current first-harmonic phase angle is less than or equal to 90 degree with medium voltage side B phase secondary current first-harmonic phase angle difference, be transformer external area error electric current or sympathetic inrush;
14 step, when C phase phase spill current
when amplitude is more than or equal to the spill current startup setting value Δ I of tranformer protection, the high-pressure side C phase secondary current area S of calculating transformer
y high-pressure side Cwith the medium voltage side C phase secondary current area S of transformer
y medium voltage side Cpoor Δ S
c, high-pressure side C phase secondary current during calculating, will be adopted
, medium voltage side C phase secondary current
, low-pressure side C phase secondary current
;
High-pressure side C phase secondary current area S
y high-pressure side Cwith the medium voltage side C phase secondary current area S of transformer
y medium voltage side Ccomputational methods and the 8th step high-pressure side secondary current area S
y high-pressure side Awith medium voltage side A phase secondary current area S
y medium voltage side Acomputational methods identical, high-pressure side C phase secondary current area S
y high-pressure side Cwith medium voltage side C phase secondary current area S
y medium voltage side Cdifference in areas be Δ S
c;
15 step, when C phase phase spill current
when amplitude is more than or equal to the spill current startup setting value Δ I of tranformer protection, calculate high-pressure side C phase secondary current first-harmonic phase angle and medium voltage side C phase secondary current first-harmonic phase angle, the high-pressure side C phase secondary current after the 4th step will be adopted during calculating whole simultaneously
, medium voltage side C phase secondary current
, low-pressure side C phase secondary current
;
16 step, as high-pressure side C phase secondary current area S
y high-pressure side Cwith medium voltage side C phase secondary current area S
y medium voltage side Cdifference in areas Δ S
cbe more than or equal to C phase secondary current difference in areas setting value S
c, and, when high-pressure side C phase secondary current first-harmonic phase angle is greater than 90 degree with medium voltage side C phase secondary current first-harmonic phase angle difference, be transformer troubles inside the sample space electric current; As high-pressure side C phase secondary current area S
y high-pressure side Cwith medium voltage side C phase secondary current area S
y medium voltage side Cdifference in areas Δ S
cbe more than or equal to C phase secondary current difference in areas setting value S
c, and, when high-pressure side C phase secondary current first-harmonic phase angle is less than or equal to 90 degree with medium voltage side C phase secondary current first-harmonic phase angle difference, be transformer external area error electric current or sympathetic inrush.
The present invention can accurately differentiate transformer fault electric current and sympathetic inrush, avoids the misoperation of transformer differential protection, ensure that the normal operation of electrical network main equipment.
Accompanying drawing explanation
Fig. 1 is transformer each side first and second electric current positive direction schematic diagram of invention.
Embodiment
Below in conjunction with accompanying drawing, the present invention is described in detail:
Sympathetic inrush in tranformer protection and a discrimination method for fault current, comprise the following steps:
The high-pressure side secondary current sampled value of the transformer of the first step, acquisition Y-Y-Δ wiring patterns, obtains the medium voltage side secondary current sampled value of the transformer of Y-Y-Δ wiring patterns, obtains the low-pressure side secondary current sampled value of the transformer of Y-Y-Δ wiring patterns;
Second step, the high-pressure side secondary current sampled value by obtaining, medium voltage side secondary current sampled value and low-pressure side secondary current sampled value, carry out differential filtering respectively;
3rd step, by the high-pressure side secondary current sampled value after differential filtering, the medium voltage side secondary current sampled value after differential filtering and the low-pressure side secondary current sampled value after differential filtering, carry out all-wave Fourier digital filtering respectively, obtain high voltage side of transformer secondary current fundamental voltage amplitude and phase angle, transformer medium voltage side secondary current fundamental voltage amplitude and phase angle, step down side secondary current fundamental voltage amplitude and phase angle;
The computational methods of high-pressure side secondary current fundamental voltage amplitude and phase angle are:
The sampling number first setting the every cycle of high voltage side of transformer secondary current is N, then the current sampling data of high voltage side of transformer secondary current sampled point is
i(
k),
k=0,1,2 ... N-1, the sampling interval is Δ t;
According to following Fourier transform formula:
Wherein:
ωthe angular frequency of-high voltage side of transformer secondary current cycle;
After obtaining the sinusoidal coefficients of first-harmonic, then the plural form of fundametal compoment is:
High-pressure side secondary current fundamental voltage amplitude is:
High-pressure side secondary current first-harmonic phase angle is:
Utilize above same method, calculate transformer medium voltage side secondary current fundamental voltage amplitude and phase angle, and step down side secondary current fundamental voltage amplitude and phase angle;
4th step, utilize Y-Δ transform method, adjustment transformer each side current amplitude and phase angle; The high-pressure side secondary current of the Y connection of the transformer of Y-Y-Δ wiring patterns is converted to the high-pressure side secondary current of Δ connection, the medium voltage side secondary current of the Y connection of the transformer of Y-Y-Δ wiring patterns is converted to the medium voltage side secondary current of Δ connection, the low-pressure side secondary current side of the Δ connection of the transformer of Y-Y-Δ wiring patterns is constant; Transformer medium voltage side current amplitude is converted to high voltage side of transformer according to transformer voltage ratio, step down side current amplitude is converted to high voltage side of transformer according to transformer voltage ratio; Obtain after filtering and conversion thus: high-pressure side A phase secondary current
, high-pressure side B phase secondary current
, high-pressure side C phase secondary current
, medium voltage side A phase secondary current
, medium voltage side B phase secondary current
, medium voltage side C phase secondary current
, low-pressure side A phase secondary current
, low-pressure side B phase secondary current
, low-pressure side C phase secondary current
;
The spill current of the tranformer protection of the 5th step, acquisition Y-Y-Δ wiring patterns starts setting value Δ I;
6th step, calculating A phase phase spill current
, B phase phase spill current
with C phase phase spill current
, computing formula is as follows:
7th step, to obtain respectively: the A phase secondary current difference in areas setting value S of the high-pressure side A phase secondary current area of transformer and the medium voltage side A phase secondary current difference in areas of transformer
a; The B phase secondary current difference in areas setting value S of the high-pressure side B phase secondary current area of transformer and the medium voltage side B phase secondary current difference in areas of transformer
b; The C phase secondary current difference in areas setting value S of the high-pressure side C phase secondary current area of transformer and the medium voltage side C phase secondary current difference in areas of transformer
c;
8th step, when A phase phase spill current
when amplitude is more than or equal to the spill current startup setting value Δ I of tranformer protection, the high-pressure side A phase secondary current area S of calculating transformer
y high-pressure side Awith the medium voltage side A phase secondary current area S of transformer
y medium voltage side Apoor Δ S
a, high-pressure side A phase secondary current during calculating, will be adopted
, medium voltage side A phase secondary current
, low-pressure side A phase secondary current
;
High-pressure side secondary current area S
y high-pressure side Acomputational methods be:
The sampling number first setting the every cycle of high voltage side of transformer electric current is N, the current sampling data of high voltage side of transformer current sample point
i(
k),
k=0,1,2 ... N-1, the sampling interval is Δ t, and utilize rectangle (or trapezoidal) method, calculate the spacer area between two sampled points, computing formula is as follows:
Δ
S 0=
i(0)*Δ
t；
Δ
S 1=
i(1)*Δ
t；
Δ
S 2=
i(2)*Δ
t；
……；
Δ
S N-1
=
i(
N-1)*Δ
t；
The sampled point that acquisition phase spill current is more than or equal to the spill current startup setting value Δ I moment of tranformer protection is
x;
Then
ymoment high voltage side of transformer A phase secondary current area:
Medium voltage side A phase secondary current area S
y medium voltage side Acomputational methods be:
The sampling number first setting the every cycle of transformer medium voltage side electric current is N, the current sampling data of transformer medium voltage side current sample point
i(
k),
k=0,1,2 ... N-1, the sampling interval is Δ t, and utilize rectangle (or trapezoidal) method, calculate the spacer area between two sampled points, computing formula is as follows:
Δ
S 0=
i(0)*Δ
t；
Δ
S 1=
i(1)*Δ
t；
Δ
S 2=
i(2)*Δ
t；
……；
Δ
S N-1
=
i(
N-1)*Δ
t；
The sampled point that acquisition phase spill current is more than or equal to the spill current startup setting value Δ I moment of tranformer protection is
x;
Then
ymoment transformer medium voltage side A phase secondary current area:
High-pressure side A phase secondary current area S
y high-pressure side Awith medium voltage side A phase secondary current area S
y medium voltage side Adifference in areas be Δ S
a;
9th step, when A phase phase spill current
when amplitude is more than or equal to the spill current startup setting value Δ I of transformer, calculate high-pressure side A phase secondary current first-harmonic phase angle and medium voltage side A phase secondary current first-harmonic phase angle, the high-pressure side A phase secondary current after the 4th step will be adopted during calculating whole simultaneously
, medium voltage side A phase secondary current
, low-pressure side A phase secondary current
;
Tenth step, as high-pressure side A phase secondary current area S
y high-pressure side Awith medium voltage side A phase secondary current area S
y medium voltage side Adifference in areas Δ S
abe more than or equal to A phase secondary current difference in areas setting value S
a, and, when high-pressure side A phase secondary current first-harmonic phase angle is greater than 90 degree with medium voltage side A phase secondary current first-harmonic phase angle difference, be transformer troubles inside the sample space electric current; As high-pressure side A phase secondary current area S
y high-pressure side Awith medium voltage side A phase secondary current area S
y medium voltage side Adifference in areas Δ S
abe more than or equal to A phase secondary current difference in areas setting value S
a, and, when high-pressure side A phase secondary current first-harmonic phase angle is less than or equal to 90 degree with medium voltage side A phase secondary current first-harmonic phase angle difference, be transformer external area error electric current or sympathetic inrush;
11 step, when B phase phase spill current
when amplitude is more than or equal to the spill current startup setting value Δ I of tranformer protection, the high-pressure side B phase secondary current area S of calculating transformer
y high-pressure side Bwith the medium voltage side B phase secondary current area S of transformer
y medium voltage side Bpoor Δ S
b, high-pressure side B phase secondary current during calculating, will be adopted
, medium voltage side B phase secondary current
, low-pressure side B phase secondary current
;
High-pressure side B phase secondary current area S
y high-pressure side Bwith the medium voltage side B phase secondary current area S of transformer
y medium voltage side Bcomputational methods and the 8th step high-pressure side A phase secondary current area S
y high-pressure side Awith medium voltage side A phase secondary current area S
y medium voltage side Acomputational methods identical, high-pressure side B phase secondary current area S
y high-pressure side Bwith medium voltage side B phase secondary current area S
y medium voltage side Bdifference in areas be Δ S
b;
12 step, when B phase phase spill current
when amplitude is more than or equal to the spill current startup setting value Δ I of tranformer protection, calculate high-pressure side B phase secondary current first-harmonic phase angle and medium voltage side B phase secondary current first-harmonic phase angle, the high-pressure side B phase secondary current after the 4th step will be adopted during calculating whole simultaneously
, medium voltage side B phase secondary current
, low-pressure side A phase secondary current
;
13 step, as high-pressure side B phase secondary current area S
y high-pressure side Bwith medium voltage side B phase secondary current area S
y medium voltage side Bdifference in areas Δ S
bbe more than or equal to B phase secondary current difference in areas setting value S
b, and, when high-pressure side B phase secondary current first-harmonic phase angle is greater than 90 degree with medium voltage side B phase secondary current first-harmonic phase angle difference, be transformer troubles inside the sample space electric current; As high-pressure side B phase secondary current area S
y high-pressure side Bwith medium voltage side B phase secondary current area S
y medium voltage side Bdifference in areas Δ S
bbe more than or equal to B phase secondary current difference in areas setting value S
b, and, when high-pressure side B phase secondary current first-harmonic phase angle is less than or equal to 90 degree with medium voltage side B phase secondary current first-harmonic phase angle difference, be transformer external area error electric current or sympathetic inrush;
14 step, when C phase phase spill current
when amplitude is more than or equal to the spill current startup setting value Δ I of tranformer protection, the high-pressure side C phase secondary current area S of calculating transformer
y high-pressure side Cwith the medium voltage side C phase secondary current area S of transformer
y medium voltage side Cpoor Δ S
c, high-pressure side C phase secondary current during calculating, will be adopted
, medium voltage side C phase secondary current
, low-pressure side C phase secondary current
;
High-pressure side C phase secondary current area S
y high-pressure side Cwith the medium voltage side C phase secondary current area S of transformer
y medium voltage side Ccomputational methods and the 8th step high-pressure side secondary current area S
y high-pressure side Awith medium voltage side A phase secondary current area S
y medium voltage side Acomputational methods identical, high-pressure side C phase secondary current area S
y high-pressure side Cwith medium voltage side C phase secondary current area S
y medium voltage side Cdifference in areas be Δ S
c;
15 step, when C phase phase spill current
when amplitude is more than or equal to the spill current startup setting value Δ I of tranformer protection, calculate high-pressure side C phase secondary current first-harmonic phase angle and medium voltage side C phase secondary current first-harmonic phase angle, the high-pressure side C phase secondary current after the 4th step will be adopted during calculating whole simultaneously
, medium voltage side C phase secondary current
, low-pressure side C phase secondary current
;
16 step, as high-pressure side C phase secondary current area S
y high-pressure side Cwith medium voltage side C phase secondary current area S
y medium voltage side Cdifference in areas Δ S
cbe more than or equal to C phase secondary current difference in areas setting value S
c, and, when high-pressure side C phase secondary current first-harmonic phase angle is greater than 90 degree with medium voltage side C phase secondary current first-harmonic phase angle difference, be transformer troubles inside the sample space electric current; As high-pressure side C phase secondary current area S
y high-pressure side Cwith medium voltage side C phase secondary current area S
y medium voltage side Cdifference in areas Δ S
cbe more than or equal to C phase secondary current difference in areas setting value S
c, and, when high-pressure side C phase secondary current first-harmonic phase angle is less than or equal to 90 degree with medium voltage side C phase secondary current first-harmonic phase angle difference, be transformer external area error electric current or sympathetic inrush.
During for transformer medium voltage side or low-pressure side non-transformer, the composite voltage (low-voltage and negative sequence voltage) of transformer three side can be utilized to form or high-pressure side secondary current phase angle in logic de the tenth step, the 13 step and the 16 step and the condition of medium voltage side secondary current phase angle difference; Can avoid like this, when troubles inside the sample space, tripping occurs;
The computational methods of low-voltage and negative sequence voltage are:
Fundamental voltage can utilize the all-wave Fourier digital filtering of the 3rd step, leaches fundamental voltage;
Positive and negative sequence voltage computational methods are:
Wherein:
a=e j120 °
for the vector calculus factor;
When transformer medium voltage side non-transformer; can be passed through composite voltage (low-voltage and negative sequence voltage) unlocking, now only need Cutoff current difference in areas to exceed setting value, no longer differentiate high pressure side current angle; protective device and exportable trip signal, tripping transformer each side circuit breaker.Have power conditions for step down side, above-mentioned conclusion can be drawn equally, but now angle to be determined as high and low pressure side current angle poor.
Utilizing Y-Δ to convert the current conversion of transformer Y side is Δ; Δ side is constant, and adjustment transformer each side current amplitude and phase place, then calculate spill current; For the transformer of Y-Y-Δ-11 wiring patterns, its current transformation formula is as following table:
Following formula is utilized to calculate spill current:
In formula:
,
,
-be A, B, C phase spill current;
,
,
-be high voltage side of transformer A, B, C phase current before conversion;
,
,
-be transformer medium voltage side A, B, C phase current before conversion;
,
,
-be high voltage side of transformer A, B, C phase current after conversion;
,
,
-be transformer medium voltage side A, B, C phase current after conversion;
,
,
-be step down side A, B, C phase current;
The transformer of other wiring groups, according to transformer each side phase condition, can derive its transformation for mula equally.
S
a, S
band S
csetting value according to transformer connecting system situation calculate after adjust.
Adjusting of Δ I is adjusted with reference to current transformer differential protection setting principle.
Claims (1)
1. the sympathetic inrush in tranformer protection and a discrimination method for fault current, comprise the following steps:
The high-pressure side secondary current sampled value of the transformer of the first step, acquisition Y-Y-Δ wiring patterns, obtains the medium voltage side secondary current sampled value of the transformer of Y-Y-Δ wiring patterns, obtains the low-pressure side secondary current sampled value of the transformer of Y-Y-Δ wiring patterns;
Second step, the high-pressure side secondary current sampled value by obtaining, medium voltage side secondary current sampled value and low-pressure side secondary current sampled value, carry out differential filtering respectively;
3rd step, by the high-pressure side secondary current sampled value after differential filtering, the medium voltage side secondary current sampled value after differential filtering and the low-pressure side secondary current sampled value after differential filtering, carry out all-wave Fourier digital filtering respectively, obtain high voltage side of transformer secondary current fundamental voltage amplitude and phase angle, transformer medium voltage side secondary current fundamental voltage amplitude and phase angle, step down side secondary current fundamental voltage amplitude and phase angle;
The computational methods of high-pressure side secondary current fundamental voltage amplitude and phase angle are:
The sampling number first setting the every cycle of high voltage side of transformer secondary current is N, then the current sampling data of high voltage side of transformer secondary current sampled point is
i(
k),
k=0,1,2 ... N-1, the sampling interval is Δ t;
According to following Fourier transform formula:
Wherein:
ωthe angular frequency of-high voltage side of transformer secondary current cycle;
After obtaining the sinusoidal coefficients of first-harmonic, then the plural form of fundametal compoment is:
High-pressure side secondary current fundamental voltage amplitude is:
High-pressure side secondary current first-harmonic phase angle is:
Utilize above same method, calculate transformer medium voltage side secondary current fundamental voltage amplitude and phase angle, and step down side secondary current fundamental voltage amplitude and phase angle;
4th step, utilize Y-Δ transform method, adjustment transformer each side current amplitude and phase angle; The high-pressure side secondary current of the Y connection of the transformer of Y-Y-Δ wiring patterns is converted to the high-pressure side secondary current of Δ connection, the medium voltage side secondary current of the Y connection of the transformer of Y-Y-Δ wiring patterns is converted to the medium voltage side secondary current of Δ connection, the low-pressure side secondary current side of the Δ connection of the transformer of Y-Y-Δ wiring patterns is constant; Transformer medium voltage side current amplitude is converted to high voltage side of transformer according to transformer voltage ratio, step down side current amplitude is converted to high voltage side of transformer according to transformer voltage ratio; Obtain after filtering and conversion thus: high-pressure side A phase secondary current
, high-pressure side B phase secondary current
, high-pressure side C phase secondary current
, medium voltage side A phase secondary current
, medium voltage side B phase secondary current
, medium voltage side C phase secondary current
, low-pressure side A phase secondary current
, low-pressure side B phase secondary current
, low-pressure side C phase secondary current
;
The spill current of the tranformer protection of the 5th step, acquisition Y-Y-Δ wiring patterns starts setting value Δ
i;
6th step, calculating A phase phase spill current
, B phase phase spill current
with C phase phase spill current
, computing formula is as follows:
7th step, to obtain respectively: the A phase secondary current difference in areas setting value S of the high-pressure side A phase secondary current area of transformer and the medium voltage side A phase secondary current difference in areas of transformer
a; The B phase secondary current difference in areas setting value S of the high-pressure side B phase secondary current area of transformer and the medium voltage side B phase secondary current difference in areas of transformer
b; The C phase secondary current difference in areas setting value S of the high-pressure side C phase secondary current area of transformer and the medium voltage side C phase secondary current difference in areas of transformer
c;
8th step, when A phase phase spill current
the spill current that amplitude is more than or equal to tranformer protection starts setting value Δ
itime, the high-pressure side A phase secondary current area S of calculating transformer
y high-pressure side Awith the medium voltage side A phase secondary current area S of transformer
y medium voltage side Apoor Δ S
a, high-pressure side A phase secondary current during calculating, will be adopted
, medium voltage side A phase secondary current
, low-pressure side A phase secondary current
;
High-pressure side secondary current area S
y high-pressure side Acomputational methods be:
The sampling number first setting the every cycle of high voltage side of transformer electric current is N, the current sampling data of high voltage side of transformer current sample point
i(
k),
k=0,1,2 ... N-1, the sampling interval is Δ
t, utilize rectangle (or trapezoidal) method, calculate the spacer area between two sampled points, computing formula is as follows:
Δ
S 0=
i(0)*Δ
t；
Δ
S 1=
i(1)*Δ
t；
Δ
S 2=
i(2)*Δ
t；
……；
Δ
S N-1
=
i(
N-1)*Δ
t；
Obtain the spill current startup setting value Δ that phase spill current is more than or equal to tranformer protection
ithe sampled point in moment is
x;
Then
ymoment high voltage side of transformer A phase secondary current area:
Medium voltage side A phase secondary current area S
y medium voltage side Acomputational methods be:
The sampling number first setting the every cycle of transformer medium voltage side electric current is N, the current sampling data of transformer medium voltage side current sample point
i(
k),
k=0,1,2 ... N-1, the sampling interval is Δ t, and utilize rectangle (or trapezoidal) method, calculate the spacer area between two sampled points, computing formula is as follows:
Δ
S 0=
i(0)*Δ
t；
Δ
S 1=
i(1)*Δ
t；
Δ
S 2=
i(2)*Δ
t；
……；
Δ
S N-1
=
i(
N-1)*Δ
t；
Obtain the spill current startup setting value Δ that phase spill current is more than or equal to tranformer protection
ithe sampled point in moment is
x;
Then
ymoment transformer medium voltage side A phase secondary current area:
High-pressure side A phase secondary current area S
y high-pressure side Awith medium voltage side A phase secondary current area S
y medium voltage side Adifference in areas be Δ S
a ;
9th step, when A phase phase spill current
the spill current that amplitude is more than or equal to transformer starts setting value Δ
itime, calculate high-pressure side A phase secondary current first-harmonic phase angle and medium voltage side A phase secondary current first-harmonic phase angle, the high-pressure side A phase secondary current after the 4th step will be adopted during calculating whole simultaneously
, medium voltage side A phase secondary current
, low-pressure side A phase secondary current
;
Tenth step, as high-pressure side A phase secondary current area S
y high-pressure side Awith medium voltage side A phase secondary current area S
y medium voltage side Adifference in areas Δ S
abe more than or equal to A phase secondary current difference in areas setting value S
a, and, when high-pressure side A phase secondary current first-harmonic phase angle is greater than 90 degree with medium voltage side A phase secondary current first-harmonic phase angle difference, be transformer troubles inside the sample space electric current; As high-pressure side A phase secondary current area S
y high-pressure side Awith medium voltage side A phase secondary current area S
y medium voltage side Adifference in areas Δ S
abe more than or equal to A phase secondary current difference in areas setting value S
a, and, when high-pressure side A phase secondary current first-harmonic phase angle is less than or equal to 90 degree with medium voltage side A phase secondary current first-harmonic phase angle difference, be transformer external area error electric current or sympathetic inrush;
11 step, when B phase phase spill current
when amplitude is more than or equal to the spill current startup setting value Δ I of tranformer protection, the high-pressure side B phase secondary current area S of calculating transformer
y high-pressure side Bwith the medium voltage side B phase secondary current area S of transformer
y medium voltage side Bpoor Δ S
b, high-pressure side B phase secondary current during calculating, will be adopted
, medium voltage side B phase secondary current
, low-pressure side B phase secondary current
;
High-pressure side B phase secondary current area S
y high-pressure side Bwith the medium voltage side B phase secondary current area S of transformer
y medium voltage side Bcomputational methods and the 8th step high-pressure side A phase secondary current area S
y high-pressure side Awith medium voltage side A phase secondary current area S
y medium voltage side Acomputational methods identical, high-pressure side B phase secondary current area S
y high-pressure side Bwith medium voltage side B phase secondary current area S
y medium voltage side Bdifference in areas be Δ S
b;
12 step, when B phase phase spill current
when amplitude is more than or equal to the spill current startup setting value Δ I of tranformer protection, calculate high-pressure side B phase secondary current first-harmonic phase angle and medium voltage side B phase secondary current first-harmonic phase angle, the high-pressure side B phase secondary current after the 4th step will be adopted during calculating whole simultaneously
, medium voltage side B phase secondary current
, low-pressure side A phase secondary current
;
13 step, as high-pressure side B phase secondary current area S
y high-pressure side Bwith medium voltage side B phase secondary current area S
y medium voltage side Bdifference in areas Δ S
bbe more than or equal to B phase secondary current difference in areas setting value S
b, and, when high-pressure side B phase secondary current first-harmonic phase angle is greater than 90 degree with medium voltage side B phase secondary current first-harmonic phase angle difference, be transformer troubles inside the sample space electric current; As high-pressure side B phase secondary current area S
y high-pressure side Bwith medium voltage side B phase secondary current area S
y medium voltage side Bdifference in areas Δ S
bbe more than or equal to B phase secondary current difference in areas setting value S
b, and, when high-pressure side B phase secondary current first-harmonic phase angle is less than or equal to 90 degree with medium voltage side B phase secondary current first-harmonic phase angle difference, be transformer external area error electric current or sympathetic inrush;
14 step, when C phase phase spill current
when amplitude is more than or equal to the spill current startup setting value Δ I of tranformer protection, the high-pressure side C phase secondary current area S of calculating transformer
y high-pressure side Cwith the medium voltage side C phase secondary current area S of transformer
y medium voltage side Cpoor Δ S
c, high-pressure side C phase secondary current during calculating, will be adopted
, medium voltage side C phase secondary current
, low-pressure side C phase secondary current
;
High-pressure side C phase secondary current area S
y high-pressure side Cwith the medium voltage side C phase secondary current area S of transformer
y medium voltage side Ccomputational methods and the 8th step high-pressure side secondary current area S
y high-pressure side Awith medium voltage side A phase secondary current area S
y medium voltage side Acomputational methods identical, high-pressure side C phase secondary current area S
y high-pressure side Cwith medium voltage side C phase secondary current area S
y medium voltage side Cdifference in areas be Δ S
c;
15 step, when C phase phase spill current
the spill current that amplitude is more than or equal to tranformer protection starts setting value Δ
itime, calculate high-pressure side C phase secondary current first-harmonic phase angle and medium voltage side C phase secondary current first-harmonic phase angle, the high-pressure side C phase secondary current after the 4th step will be adopted during calculating whole simultaneously
, medium voltage side C phase secondary current
, low-pressure side C phase secondary current
;
16 step, as high-pressure side C phase secondary current area S
y high-pressure side Cwith medium voltage side C phase secondary current area S
y medium voltage side Cdifference in areas Δ S
cbe more than or equal to C phase secondary current difference in areas setting value S
c, and, when high-pressure side C phase secondary current first-harmonic phase angle is greater than 90 degree with medium voltage side C phase secondary current first-harmonic phase angle difference, be transformer troubles inside the sample space electric current; As high-pressure side C phase secondary current area S
y high-pressure side Cwith medium voltage side C phase secondary current area S
y medium voltage side Cdifference in areas Δ S
cbe more than or equal to C phase secondary current difference in areas setting value S
c, and, when high-pressure side C phase secondary current first-harmonic phase angle is less than or equal to 90 degree with medium voltage side C phase secondary current first-harmonic phase angle difference, be transformer external area error electric current or sympathetic inrush.
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| CN116404612A (en) * | 2023-06-06 | 2023-07-07 | 三峡智能工程有限公司 | Method and system for preventing generator differential protection misoperation caused by emergency current |
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| CN116404612A (en) * | 2023-06-06 | 2023-07-07 | 三峡智能工程有限公司 | Method and system for preventing generator differential protection misoperation caused by emergency current |
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