CN101752835A - Transformer compound current differential protection method and compound current differential relay - Google Patents
Transformer compound current differential protection method and compound current differential relay Download PDFInfo
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Abstract
The invention discloses a compound current differential protection method and a compound current differential relay for stable state quantity and fault component of the internal fault of a transformer. Because a conventional stable state quantity differential relay has insufficient sensitivity when a turn-to-turn fault occurs to a transformer body due to the heavy load of the transformer or when an external fault converts into an internal turn-to-turn fault (the external and the internal coexist), the invention provides the compound current differential protection method and the differential relay based on the stable state quantity and the fault component. In the relay, a stable state quantity double K differential relay is formed by adopting the stable state quantity to compute a differential current and brake a current, and another fault component double K differential relay is formed by adopting the fault component (a phase current, a mutation negative-sequence current, and a zero-sequence current) to computer the differential current and brake the current. The two differential relay is combined into the compound current differential relay of the stable state quantity and the fault component. Test results show that the differential protection method and the relay based on the method has excellent sensitivity, safety and rapidity.
Description
Technical Field
The invention belongs to the field of transformer protection in the relay protection technology, and particularly relates to a transformer differential protection method and a differential relay.
Background
At present, when a transformer body inter-turn fault occurs in a heavy load of a transformer or an external fault is converted into an internal inter-turn fault (the external fault exists in the external area), because a load current or an external through current is large and is mostly a brake current, and a fault current is relatively small and is mainly a differential current in the inter-turn fault, the stable-state differential protection relay is not sensitive enough and cannot act.
If the method of reducing the rate braking coefficient K is adopted, the differential protection may be mistaken due to factors such as inconsistent transmission characteristics of CTs on all sides of the transformer, transient errors of the CTs and the like when an external fault occurs, and the safety of the differential protection is sacrificed. The proportional braking coefficient K must therefore be conditionally adjusted to decrease during an in-zone fault and increase otherwise, thus increasing the sensitivity of the differential relay without affecting its safety.
Disclosure of Invention
The invention provides a transformer composite current differential protection method and a composite current differential relay based on steady-state quantity and fault component, which aim to solve the problem that in the prior art, when transformer body turn-to-turn fault occurs in transformer overload or when an external fault is converted into an internal turn-to-turn fault (existing in an external area at the same time), the sensitivity of the transformer steady-state quantity differential protection relay is not enough, and the safety of the relay must be considered.
The invention discloses a transformer composite current differential protection method based on steady-state quantity and fault component, which comprises the following steps:
a transformer composite current differential protection method based on steady-state quantity and fault component is characterized by comprising the following steps:
(1) measuring and calculating steady-state quantity current and fault component current of each side of the transformer through a current transformer of each side of the transformer, wherein the fault component current is any one of sudden change current, negative sequence current or zero sequence current;
(2) taking the side with the maximum absolute value of the steady-state quantity current of each side of the transformer as one end of steady-state quantity differential protection, and taking the sum of the steady-state quantity currents of the other sidesThe equivalent is the other end of the steady state quantity differential protection, and the currents at the two ends of the steady state quantity differential protection are respectively
The steady-state magnitude differential current is recorded as
Wherein
(3) The side with the largest absolute value of the fault component current of each side of the transformer is taken as one end of the fault component differential protection, the fault component currents of the other sides and the equivalent are taken as the other end of the fault component differential protection, and the currents at the two ends of the fault component differential protection are respectively
Differential current of fault component is noted
Wherein
(4) When the following transformer composite current differential protection action equation, the steady-state quantity differential protection additional condition and the fault component differential protection additional condition are simultaneously met, the transformer composite current differential protection acts:
K，k，k1in order to be the braking coefficient,
k ranges from 0.5 to 2;
k ranges from 0.1 to 1;
k1the value range is 0.1-1;
Iseta threshold value set for steady state quantity differential protection;
FIsetand the threshold values are respectively set for the mutation quantity, the negative sequence and the zero sequence additional condition.
According to the differential protection method, the invention further discloses a transformer composite current differential relay based on steady-state quantity and fault component, the composite current differential relay adopts steady-state quantity to calculate differential current and brake current to form a steady-state quantity double-K differential relay, adopts fault component current to calculate differential current and brake current to form another differential relay with fault component additional condition, wherein the fault component current is any one of sudden change current, negative sequence current or zero sequence current; when the composite current differential relay meets the composite current differential protection action equation, the additional condition of transformer steady-state quantity differential protection and the additional condition of transformer fault component differential protection, the relay acts.
The method for implementing the composite current differential relay is further preferably, but not limited to, implemented in the following manner:
(1) converting a multi-sided differential into a two-sided differential
The method of converting the multi-side differential motion into the two-side differential motion is adopted.
Steady state quantity differential:
and finding the side with the maximum absolute value of the steady-state quantity current in the multiple sides, setting the side as one end, and setting the steady-state quantity current sum of the other sides as the other end. M and sigma-M are named separately, often as subscripts to the current.
-steady state magnitude current maximum side current in each side
The fault component comprising a phase current surge quantity
Negative sequence current
Zero sequence current
Is marked as
And finding the side with the largest absolute value of the fault component current in the multiple sides, taking the sudden change current as an example, setting the side with the largest absolute value of the sudden change current as one side, and setting the sum of the sudden change currents and the equivalent of the rest sides as the other side. M and sigma-M are named separately, often as subscripts to the current.
-mutant differential current
(2) Action equation of steady-state quantity and fault component composite current differential relay
General expression of the double-K ratio differential equation: to discharge large current in two-side current
Multiplying a small braking coefficient k; small current flow
Multiplying by a large braking coefficient K. Different braking coefficients are respectively adopted, so that the action characteristic is improved. The following formula:
the steady state magnitude split phase current differential is given by:
wherein,
is composed of
A current positive sequence component of (a);
K，k，k1in order to be the braking coefficient,
k ranges from 0.5 to 2;
k ranges from 0.1 to 1;
k1the value range is 0.1-1;
Iseta threshold value set for steady state quantity differential protection;
FIsetand the threshold values are respectively set for the mutation quantity, the negative sequence and the zero sequence additional condition. . The fault component current differential is given by:
a composite current differential relay of a steady-state quantity and a fault component is obtained by using the formula (1) multiplied by the formula (2). Let K equal 1, giving the formula:
inequality divided on both sides by
To obtain the following formula:
order to
When K < 0.5, mandatory K ═ 0.5, we obtain:
additional action conditions of the composite current differential relay:
compared with the prior art, the invention has the following advantages:
when the transformer body inter-turn fault occurs in the heavy load of the transformer or the external fault is converted into the internal inter-turn fault (the external fault exists in the external area), the sensitivity of the steady-state quantity differential protection relay is not enough and the protection cannot act because the load current or the external through current is larger and is the braking current, and the fault current is relatively smaller and is mainly the differential current in the inter-turn fault. The fault component current differential is independent of the load, and the operation performance is excellent. However, fault component current differentials also have their own problems: for example, zero sequence and negative sequence are the results of three-phase operation, and the phase cannot be selected. When a simultaneous fault occurs inside and outside the zone, if the external fault is stronger than the internal fault, the fault may be rejected. For another example, the phase current abrupt change, generally the abrupt change differential, cannot be applied for a long time, when the abrupt change is calculated, the decrement is the current, and the decrement is the current in the previous week or two weeks. In order to put the sudden variable differential into operation for a long period of time, severe limiting conditions must be added
And
the simultaneous satisfaction of these two conditions is almost an intra-zone failure. Even more, the fault component differential changes the braking coefficient of the steady-state component split-phase current differential only to a limited extent. The two types of differential mechanisms are organically combined, mutually complement and mutually restrict. In summary, fault component differentials help steady state component differentials improve sensitivity; the steady state magnitude differential helps the fault component differential to improve safety.
Drawings
Fig. 1 is a system diagram of a typical substation transformer and a differential protection range illustration;
FIG. 2 is a diagram of a typical differential relay action curve for a transformer;
FIG. 3 is a diagram of the action curve of the transformer differential relay according to the present invention;
fig. 4 is a flow chart of the function implementation of the present invention.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. Referring to fig. 1, a system diagram of a typical substation transformer and differential protection range are illustrated.
The range covered by the curve in fig. 1 is the range of protection of the differential protection relay, called an in-zone fault, and is formed by the current on each side of the transformer. An out-of-curve fault is referred to as an out-of-range fault. The dashed box in fig. 1 indicates that a winding fault in the transformer body is called an inter-turn fault.
Referring to fig. 2, a typical differential relay action curve for a transformer is shown. The action equation is as follows:
with the additional conditions:
ordinate in FIG. 2For differential current, abscissa
For braking current, IsetThe minimum action current is K, and the slope is a fixed setting value. The rate differential protection curve is an operation curve composed of a differential current and a brake current. The action area is arranged above the curve.
The invention relates to a transformer composite current differential protection method based on steady-state quantity and fault component, as shown in fig. 4, the specific implementation method is as follows:
(1) measuring and calculating steady-state quantity current and sudden-change quantity current of each side of the transformer through a current transformer of each side of the transformer, and calculating other side currents to a high-voltage side by taking the current of the high-voltage side as a reference;
and taking the current of the high-voltage side as a reference, and calculating the other sides to the high-voltage side. The equilibrium coefficients for each side were calculated as:
calculating the primary rated current of each side of the transformer:
in the formula: seThe maximum rated capacity of the transformer is obtained; u shape1eThe voltage is rated for each side of the transformer (based on the actual voltage of operation).
Calculating secondary rated current of each side of the transformer:
in the formula: i is1ePrimary rated current is provided for each side of the transformer; n isLHThe CT transformation ratio of each side of the transformer. And calculating the balance coefficients of the middle and low voltage sides of the transformer by taking the high voltage side as a reference:
and multiplying the current of each phase of the other side by the corresponding balance coefficient to obtain the current of each phase after amplitude compensation.
(2) Current phase compensation on each side
The phase of the secondary current of the CT on each side of the transformer is self-corrected by software, so that the phase is corrected on the Y side (taking an 11-point wiring transformer as an example). The correction method comprises the following steps:
y0 side: <math><mfenced open='' close='}'><mtable><mtr><mtd><msubsup><mover><mi>I</mi><mo>·</mo></mover><mi>A</mi><mo>′</mo></msubsup><mo>=</mo><mrow><mo>(</mo><msub><mover><mi>I</mi><mo>·</mo></mover><mi>A</mi></msub><mo>-</mo><msub><mover><mi>I</mi><mo>·</mo></mover><mi>B</mi></msub><mo>)</mo></mrow><mo>/</mo><msqrt><mn>3</mn></msqrt></mtd></mtr><mtr><mtd><msubsup><mover><mi>I</mi><mo>·</mo></mover><mi>B</mi><mo>′</mo></msubsup><mo>=</mo><mrow><mo>(</mo><msub><mover><mi>I</mi><mo>·</mo></mover><mi>B</mi></msub><mo>-</mo><msub><mover><mi>I</mi><mo>·</mo></mover><mi>C</mi></msub><mo>)</mo></mrow><mo>/</mo><msqrt><mn>3</mn></msqrt></mtd></mtr><mtr><mtd><msubsup><mover><mi>I</mi><mo>·</mo></mover><mi>C</mi><mo>′</mo></msubsup><mo>=</mo><mrow><mo>(</mo><msub><mover><mi>I</mi><mo>·</mo></mover><mi>C</mi></msub><mo>-</mo><msub><mover><mi>I</mi><mo>·</mo></mover><mi>A</mi></msub><mo>)</mo></mrow><mo>/</mo><msqrt><mn>3</mn></msqrt></mtd></mtr></mtable></mfenced></math>
in the formula:
is the secondary current of CT on the Y side;
the corrected phase currents for the Y side. Other connections may be analogized.
The differential current and the braking current are calculated on the basis of the current phase correction and the balance compensation.
(3) Differential current calculation
The differential current is calculated as follows:
in the formula:
is a differential current;
is the sum of all side phase currents.
(4) The method of converting the multi-side differential motion into the two-side differential motion.
1) Steady state quantity differential:
and finding the side with the maximum absolute value of the steady-state quantity current in the multiple sides, determining the side as one side, and determining the steady-state quantity current sum of the other sides as the other side. M and sigma-M are named separately, often as subscripts to the current.
2) Differential fault components (including phase current inrush magnitude)
Negative sequence current
Zero sequence current
) The following phase current abrupt change
For example, the following steps are carried out:
and finding the side with the maximum absolute value of the sudden change current in the multiple sides, and setting the side as one side, and setting the sum of the sudden change currents of the rest sides as the other side. M and sigma-M are named separately, often as subscripts to the current.
(5) The general expression of the steady-state quantity and fault component composite current differential relay action equation double-K value ratio differential equation is as follows: to discharge large current in two-side current
Multiplying a small braking coefficient k; small current flow
Multiplying by a large braking coefficient K. Different braking coefficients are respectively adopted, so that the action characteristic is improved. The following formula:
the steady state magnitude split phase current differential is given by:
wherein,
is composed of
A current positive sequence component of (a);
K，k，k1in order to be the braking coefficient,
k ranges from 0.5 to 2;
k ranges from 0.1 to 1;
k1the value range is 0.1-1;
the fault component current differential is given by:
a composite current differential relay of a steady-state quantity and a fault component is obtained by using the formula (1) multiplied by the formula (2). Let K equal 1, giving the formula:
inequality divided on both sides by
To obtain the following formula:
order to
When K < 0.5, mandatory K ═ 0.5, we obtain:
additional action conditions of the composite current differential relay:
the action curve is shown in figure 3.
From a comparison of fig. 3 and 2, it can be seen that the conventional typical rate braking curve is a fixed curve, which is constant for all conditions. The relay proposed by the invention is a cluster of curves, and the slope of the curve is adjusted according to the severity of the fault. When the transformer body inter-turn fault occurs in the heavy load of the transformer or the external fault is converted into the internal inter-turn fault (the external fault exists in the external area), the sensitivity of the steady-state quantity differential protection relay is not enough and the relay cannot act due to the fact that the load current or the external ride-through current is large and is braking current, and the fault current is relatively small in the inter-turn fault. The fault component current differential is independent of the load, and the operation performance is excellent. However, fault component current differentials also have their own problems: for example, zero sequence and negative sequence are the results of three-phase operation, and the phase cannot be selected. When a simultaneous fault occurs inside and outside the zone, if the external fault is stronger than the internal fault, the fault may be rejected. For another example, the phase current abrupt change, generally the abrupt change differential, cannot be applied for a long time, and when the abrupt change is calculated, the number to be subtracted is the current, and the number to be subtracted is the current in the previous week or two weeks, and due to the complexity of the number to be subtracted, the previous week or two weeks may have no fault, may have a fault, may oscillate, and the like. In order to put the sudden variable differential into operation for a long period of time, severe limiting conditions must be added
And
the simultaneous satisfaction of these two conditions is almost an intra-zone failure. In other words, the sudden magnitude differential changes the braking coefficient of the steady-state magnitude split-phase current differential only to a limited extent. The two types of differential mechanisms are organically combined, mutually complement and mutually restrict. In summary, fault component differentials help steady state component differentials improve sensitivity; stableThe difference in state quantities helps the difference in fault components to improve safety.
The invention also discloses a transformer composite current differential relay based on the steady state quantity and the fault component, wherein the composite current differential relay adopts the steady state quantity to calculate the differential current and the braking current to form a steady state quantity double-K differential relay, and adopts the fault component current to calculate the differential current and the braking current to form another fault component double-K differential relay; the composite current differential relay acts when it satisfies the following equation of action:
K，k，k1in order to be the braking coefficient,
k ranges from 0.5 to 2;
k ranges from 0.1 to 1;
k1the value range is 0.1-1;
Iseta threshold value set for steady state quantity differential protection;
FIsetand the threshold values are respectively set for the mutation quantity, the negative sequence and the zero sequence additional condition.
Claims (3)
1. A transformer composite current differential protection method based on steady-state quantity and fault component is characterized by comprising the following steps:
(1) measuring and calculating steady-state quantity current and fault component current of each side of the transformer through a current transformer of each side of the transformer, wherein the fault component current is any one of sudden change current, negative sequence current or zero sequence current;
(2) taking the side with the maximum absolute value of the steady-state quantity current of each side of the transformer as one end of steady-state quantity differential protection, and taking the steady-state quantities of the other sidesThe current sum is equivalently determined as the other end of the steady-state quantity differential protection, and the currents at the two ends of the steady-state quantity differential protection are respectively
The steady-state magnitude differential current is recorded as
Wherein
(3) The side with the largest absolute value of the fault component current of each side of the transformer is taken as one end of the fault component differential protection, the fault component currents of the other sides and the equivalent are taken as the other end of the fault component differential protection, and the currents at the two ends of the fault component differential protection are respectively
Differential current of fault component is noted
Wherein
(4) When the following transformer composite current differential protection action equation, the steady-state quantity differential protection additional condition and the fault component differential protection additional condition are simultaneously met, the transformer composite current differential protection acts:
wherein,
K，k，k1in order to be the braking coefficient,
the K value ranges from 0.5 to 2;
k ranges from 0.1 to 1;
k1the value range is 0.1-1;
Iseta threshold value set for steady state quantity differential protection;
FIsetthreshold values set for the fault component differential protection, respectively.
2. A transformer composite current differential relay based on steady state quantity and fault component is characterized in that the composite current differential relay adopts steady state quantity to calculate differential current and brake current to form a steady state quantity double-K differential relay, and adopts fault component current to calculate differential current and brake current to form another differential relay with fault component additional condition, wherein the fault component current is any one of sudden change current, negative sequence current or zero sequence current; when the composite current differential relay meets the composite current differential protection action equation, the additional condition of transformer steady-state quantity differential protection and the additional condition of transformer fault component differential protection, the relay acts. 3. The transformer composite current differential relay according to claim 2, characterized in that a transformer multi-side differential is converted into a two-side differential, namely:
taking the side with the maximum absolute value of the steady-state quantity current of each side of the transformer as one end of the steady-state quantity double-K differential relay, taking the steady-state quantity currents and the equivalents of the other sides as the other end of the steady-state quantity double-K differential relay, and respectively recording the currents at the two ends of the steady-state quantity double-K differential relay as
The steady-state magnitude differential current is recorded as
Wherein
Using the side with the maximum absolute value of the fault component current at each side of the transformer as one end of a differential relay of the fault component additional condition, and using the fault component currents and the equivalent values at the other sides as the fault component additional conditionThe other end of the conditioned differential relay, the two-end currents of the above-mentioned fault component differential protection are respectively recorded as
Differential current of fault component is noted
Wherein
3. The transformer composite current differential relay according to claim 3, characterized in that the composite current differential protection action equation and the transformer steady state amount differential protection additional condition and the transformer fault component differential protection additional condition are preferably as follows:
wherein,is composed of
A current positive sequence component of (a);
K，k，k1in order to be the braking coefficient,
k ranges from 0.5 to 2;
k ranges from 0.1 to 1;
k1the value range is 0.1-1;
Iseta threshold value set for steady state quantity differential protection;
FIsetand the threshold values are respectively set for the mutation quantity, the negative sequence and the zero sequence additional condition.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102324722A (en) * | 2011-09-08 | 2012-01-18 | 山东大学 | Current differential protection method based on fault component current amplitudes and phase differences |
| CN102810856A (en) * | 2012-08-02 | 2012-12-05 | 中国南方电网有限责任公司超高压输电公司检修试验中心 | Phase correction method for arbitrary impulse converter transformer current difference |
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| CN102324722A (en) * | 2011-09-08 | 2012-01-18 | 山东大学 | Current differential protection method based on fault component current amplitudes and phase differences |
| CN102810856A (en) * | 2012-08-02 | 2012-12-05 | 中国南方电网有限责任公司超高压输电公司检修试验中心 | Phase correction method for arbitrary impulse converter transformer current difference |
| CN102810856B (en) * | 2012-08-02 | 2015-04-08 | 中国南方电网有限责任公司超高压输电公司检修试验中心 | Phase correction method for arbitrary impulse converter transformer current difference |
| CN105140892A (en) * | 2015-07-21 | 2015-12-09 | 河南行知专利服务有限公司 | Line protection method for power transmission line |
| CN105529688B (en) * | 2016-02-25 | 2018-03-16 | 三峡大学 | Transformer excitation flow and failure difference stream recognition method based on Hausdorff distance algorithms |
| CN105529688A (en) * | 2016-02-25 | 2016-04-27 | 三峡大学 | Transformer excitation inrush current and fault differential current recognition method based on Hausdorff distance algorithm |
| CN106356822A (en) * | 2016-10-10 | 2017-01-25 | 许继集团有限公司 | Underreach combined type protection method and device for semi-wavelength power transmission line |
| CN106356822B (en) * | 2016-10-10 | 2019-02-05 | 许继集团有限公司 | A kind of deficient range combinations formula guard method of half-wave power transmission route and device |
| CN109507520A (en) * | 2018-12-20 | 2019-03-22 | 国网北京市电力公司 | Turn-to-turn fault detection method, device, storage medium and the processor of transformer |
| CN110299692A (en) * | 2019-07-10 | 2019-10-01 | 许昌许继软件技术有限公司 | A kind of converter power transformer differential protecting method and device |
| CN113671315A (en) * | 2021-08-18 | 2021-11-19 | 北京四方继保工程技术有限公司 | ITn power supply insulation fault positioning method based on proportional differential principle |
| CN113671315B (en) * | 2021-08-18 | 2023-10-27 | 北京四方继保工程技术有限公司 | ITn power supply insulation fault positioning method based on proportional differential principle |
| CN114172134A (en) * | 2021-12-14 | 2022-03-11 | 四方继保（武汉）软件有限公司 | Differential protection self-synchronization method and system based on waveform zero crossing point before fault |
| CN114172134B (en) * | 2021-12-14 | 2024-05-24 | 四方继保（武汉）软件有限公司 | Differential protection self-synchronization method and system based on zero crossing point of pre-fault waveform |
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