RU2705517C1 - Stand for calculation of short circuit currents of inter-substation zone of traction ac network - Google Patents

Stand for calculation of short circuit currents of inter-substation zone of traction ac network Download PDF

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RU2705517C1
RU2705517C1 RU2018146585A RU2018146585A RU2705517C1 RU 2705517 C1 RU2705517 C1 RU 2705517C1 RU 2018146585 A RU2018146585 A RU 2018146585A RU 2018146585 A RU2018146585 A RU 2018146585A RU 2705517 C1 RU2705517 C1 RU 2705517C1
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short
traction
circuit
power supply
resistances
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RU2018146585A
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Леонид Абрамович Герман
Камиль Субханвердиевич Субханвердиев
Александр Сергеевич Серебряков
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Федеральное государственное бюджетное образовательное учреждение высшего образования "Российский университет транспорта (МИИТ)" РУТ (МИИТ)
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Abstract

FIELD: electricity.
SUBSTANCE: invention relates to electric power supply system of AC traction network, namely to development of stand for calculation of short circuit currents of inter-substation section of traction AC network with two-way power supply. Essence: test bench circuit includes power supply unit and node mutual resistance Z1 of two units 110(220) kV of traction substations. One output of power supply is connected to the third beam of three-beam star of resistance of short circuit. Other output of power supply is connected to the first output of mutual resistance Z1, the second output of which is connected to connected to the second outputs Z2 and Z3 of supply lines 110(220) kV.
EFFECT: reduced error in calculation of short-circuit currents of feed lines of the overhead system, namely, obtaining accurate values of short-circuit currents of supply lines of traction substations and sectioning stations, which are necessary for high-quality adjustment and comprehensive analysis of relay protection behavior.
1 cl, 4 dwg

Description

"The technical field to which the invention relates"
The invention relates to a power supply system for a traction AC network, namely, the development of a stand for calculating short circuit currents in a traction AC network of an inter-substation zone with two-way power supply.
"Prior art"
In [1], a physical model of the electric railway was proposed, which makes it possible to determine short-circuit currents (SC) in the traction network. The disadvantage of the model: the parameters of the specific six 110 kV lines (resistance, inductance and capacitance) are mounted in it for supplying three traction substations and it is not possible to change the power supply schemes of traction substations.
In normative documents [2, 3], for calculating short circuit parameters, an equivalent substitution scheme for the inter-substation zone with two traction substations is proposed for the formation of two-way power supply to the traction network. In it, the resistance of the traction substation is represented by the sum of the resistances of the step-down transformers and the resistances of the power system - an external power supply system (SVE). As a rule, when designing and operating, there is no scheme of the external power supply system and its parameters, and the information on the LEA from the power systems is limited to data on the short-circuit power on the 110 (220) kV buses of traction substations. This explains that in [2, 3] it is proposed to determine the LES parameters by the short-circuit power on the tires of traction substations. Thus, when constructing a test bench according to the resistance data of all elements of the power supply system according to [2 and 3], it is possible to calculate short-circuit currents for any sections at given short-circuit capacities on traction substation buses. However, in this case, due to the lack of an accurate scheme of external power supply networks (LEA) of traction substations, it is necessary to adopt an approximate scheme of LEA when feeding traction substations directly with 110 (220) kV lines from the LEA power source. At the same time, in reality, of course, there is an electrical connection between these lines, which we will further define as the nodal mutual resistance of the nodes of two adjacent traction substations.
In accordance with the prototype [2, Fig. 4.1] we consider the following initial scheme for constructing the stand (it should be noted that in Fig. 4.1 the prototype of the transformer and the supply line are combined):
A stand for calculating the short circuit currents of the inter-substation zone of the AC traction network, containing two traction substations A and B with the resistances of transformers ZtA and ZtB with voltage 110 / 27.5 (220 / 27.5) for two-way power supply of the traction network, which, when short-circuited, represents the first three-beam star of resistances, the two beams of which ZтcA and ZтcB are connected to the first terminals of the resistances of the transformers ZтA and ZтB, the second terminals of which are connected to the first terminals of the equivalent resistances Z2 and Z3 of the supply lines 110 (220) kV traction stations, and the third beam of the first three-ray star includes the equivalent resistance Z AB of the short circuit.
The disadvantages of the prototype stand:
1) Lack of electrical connection between two adjacent traction substations via the SVE 110 (220) kV network, which changes the current distribution in the traction network during a short circuit;
2) Uncertainty in the choice of rated voltage at traction substations, and therefore, in calculations, as a rule, the voltage at substations is assumed to be the same.
These shortcomings lead to a methodological error in the calculation of short circuit currents in the traction network with its two-way power supply, i.e. short-circuit currents in the traction network will be, for example, 520A, but in reality 410A (an example was taken from an experiment on a real site), therefore, the error in in this case, according to the calculation of short-circuit currents in the traction network - 27%. Typically, the error with increasing distance from the power source can reach 30-40%. As a result, relay protection with unpredictable negative consequences will be incorrectly configured and will not work during short circuits.
"Disclosure of inventions"
Ways to obtain additional information on the equivalent external power supply scheme of traction substation.
The objective of the invention is to increase the accuracy of determining short-circuit currents in a traction network using a stand, for which it is proposed to perform a stand according to a new scheme in terms of an external power supply system with parameters determined by additional information from the power system.
We are talking about power from the power system of two adjacent traction substations connected to the traction network on which the short circuit occurred. Any external power supply system for two traction substations can be equivalent to a three-beam resistance star. One beam with resistance Z1 (mutual nodal resistance) is connected to a power source, and the other two beams Z2 and Z3 are connected to traction substations.
There are two ways to obtain additional information on equivalent resistances in the equivalent circuit, which will be further used in the stand.
1) All parameters of the equivalent circuit are reduced to the voltage of the traction winding of the transformer - 27.5 kV. The calculation of the resistances Z TCA , Z TCB and Z AB is given in [2], we will show here a method for calculating the resistances Z 1 , Z 2 and Z 3 .
In [4, 5], a method was proposed for experimentally determining the mutual resistance Z 1 (Ohm / phase), the essence of which is that, by experiment on traction substations, the ratio of the voltage change at the traction substation under consideration when the load on the adjacent substation is changed. Next, the resistances Z2 and Z3 (ohms per phase) are determined, for this it is necessary to subtract the value of the experimentally found mutual resistance Z1 from the eigenvalues of the resistances calculated by the short-circuit power at the inputs to the substation:
Figure 00000001
Figure 00000002
where S cA and S cB are the short-circuit capacities on the 110 (220) kV buses of the traction substations A and B;
Z22 and Z33 are the intrinsic resistances of the bus nodes of 110 (220) kV traction substations A and B (here these nodes are designated - 2 and 3).
2) Unfortunately, it is possible to determine Z1, Z2, Z3 by the above method only by experimentally determined mutual resistance Z1, which cannot be performed at the design stage.
Therefore, another way is proposed for determining the parameters of the equivalent resistance of the SVE Z1, Z2, Z3, consisting in the following.
The power system, as usual, provides data on two adjacent traction substations with data on the short-circuit capacities at the inputs of 110 (220) kV substations or short-circuit currents or input resistances. Additionally, the power system should give one more parameter: short-circuit power (short-circuit currents or input resistance) with simultaneous short-circuit at the inputs of both substations, which is quite simple to perform.
Then, during the design, the data on the required resistances will be known (see Examples below)
Figure 00000003
Figure 00000004
Figure 00000005
where - Ik1 and Ik2 - short-circuit currents of transformer inputs 110 (220) kV at short-circuit separately at each transformer of substations A and B; Ik1d and Ik2d - short-circuit currents of inputs of transformers 110 (220) kV at short-circuit simultaneously at the inputs of two indicated transformers.
To achieve the above objectives of the invention proposed:
A stand for calculating short-circuit currents of the inter-substation zone of an alternating current traction network, containing two traction substations A and B with transformer resistances ZtA and ZtB of voltage 110 / 27.5 (220 / 27.5) for two-way power supply to the traction network, which, when short-circuited ( KZ) represents the first three-beam star of resistances, two beams of which ZтcA and ZтcB are connected to the first terminals of the resistances of transformers ZтA and ZтB, the second terminals of which are connected to the first terminals of the equivalent resistances Z2 and Z3 of the supply lines 110 (220) kV traction x substations, and the third beam of the first three-ray star includes the equivalent resistance Z AB of the short circuit, while it is equipped with a power supply for the stand Uo and nodal mutual resistance Z1 of the supply lines 110 (220) kV of the second three-beam star of equivalent resistances Z1, Z2, Z3, one the output of the power source is connected to the third beam of the short circuit with the equivalent resistance Z AB of the first three-beam star of resistances, and the other output of the power source is connected to the first output of the nodal mutual resistance Z1, the second terminal of which is connected to the connected second terminals Z2 and Z3 of the supply lines 110 (220) kV, and the equivalent resistances Z1, Z2, Z3 are determined by the following mathematical expressions:
Figure 00000006
Figure 00000007
Figure 00000008
where - Ik1 and Ik2 - short-circuit currents of transformer inputs 110 (220) kV at short-circuit separately at each transformer of substations A and B; Ik1d and Ik2d - short-circuit currents of inputs of transformers 110 (220) kV at short-circuit simultaneously at the inputs of two indicated transformers.
The technical result of the claimed invention consists in significantly reducing the error in calculating the short circuit currents of the connections of the supply lines of the contact network and, as a result, obtaining the exact values of the short circuit currents of the supply lines of the traction substations and sectioning posts, necessary for high-quality tuning and a comprehensive analysis of the relay protection behavior.
"Brief Description of the Drawings"
In FIG. 1 shows the obtained circuit stand with equivalent resistance parameters of power supply elements;
In FIG. 2: short-circuit experience at the injection of a TPA transformer;
In FIG. 3: short-circuit experience at the input of the TPV transformer;
In FIG. 4: short-circuit experience at the inputs of TPA and TPV transformers at the same time.
"Implementation of the invention"
On the equivalent equivalent circuit (Fig. 1), the following notation is used:
U 0 is the voltage of the power source, V; Z tA , Z tB - resistance of step-down transformers of substations A and B, Ohm; Z tcA , Z tcB , Z AB - equivalent resistance of the traction network and the branch of equivalent short circuit resistance. Ohm; Z1 , Z2 , Z3 - equivalent resistances of the equivalent circuit equivalent circuit of the power system network (SVE), Ohm.
The calculated values of the resistances Z1 , Z2 , Z3 will serve as parameters of the equivalent circuit of the power system network and are entered into the stand as initial data. Naturally, all parameters of the resistances in the stand, and in particular, Z1 Z2 Z3 must be adjustable, since with each calculation they change depending on the parameters of the power system, traction network and the location of the short circuit.
Thus, the proposed stand with the considered resistance parameters essentially differs from the stand according to the equivalent circuit with resistances as calculated by the method from regulatory documents [2, 3]:
1) adding a power supply with a voltage of Uo to the circuit, 2) adding a nodal mutual resistance Z1 to the circuit, and 3) introducing resistance values Z1, Z2, Z3 according to the proposed expressions (3), (4), (5).
Based on the received short-circuit currents, it is easy to determine the voltages at the transformers of the traction substations (at the resistances Z tA and Z tB ). As a result, according to calculations at the bench, the specified values of short-circuit currents in the traction network are obtained and the specified values of voltages at the transformers of the traction substations are determined, in contrast to the calculations by the normative method [2, 3]. In other words, the proposed calculation of short-circuit currents at the stand is a working tool for determining short-circuit currents in the traction network and the calculation of relay protection during design, as well as a guide for operations for maintenance of power supply systems for railways of alternating current. As a result, after calculations at the stand, there is no obligatory requirement to check the short-circuit currents when the traction substation is switched on after its installation.
Examples:
For three short-circuit experiments, three-phase short-circuit diagrams are presented at the bushings of traction substation transformers:
- FIG. 2: short-circuit experience at the injection of a TPA transformer;
- FIG. 3: short-circuit experience at the input of the TPV transformer;
- FIG. 4: short-circuit experience at the inputs of TPA and TPV transformers at the same time.
In short circuit, short circuit points (shown in red) are connected to bus 0 of the power source.
Since it is supposed to obtain initial data at the time of designing the electrified site, then in FIG. 2, 3, 4 there is no traction network (i.e. Z tcA and Z tcB ).
For three short circuits, the equations of the electric state of the circuit are compiled
Figure 00000009
Figure 00000010
Figure 00000011
where Ik1 and Ik2 - short-circuit currents of inputs at short-circuit separately on each transformer A and B;
Ik1d and Ik2d - short-circuit currents of inputs at short-circuit simultaneously at the inputs of two transformers.
Solving the equations together, we define
Figure 00000012
Figure 00000013
Figure 00000014
Literature
1. Marquardt G.G. The use of probability theory and computer technology in the power supply system. M .: Transport, 1972, 224 p.
2. Guidelines for the relay protection of traction power supply systems. M .; TRANSIZDAT, 2005, - 216 p.
3. STO RZD 07.021.4-2015 “Protection of railway power supply systems against short circuits and overloads. Part 4. Methodology for the selection of protection settings in the traction power supply system of alternating current ”;
4. German L.A., Kishkurno K.V. Comparison of methods for calculating the traction power supply system for different methods of accounting for external network parameters / Vestnik VNIIZhT, 2013. No. 1. S. 16-21.
5. Patent No. 23967077. A method for determining nodal mutual resistance in a traction network of railways. German L.A. Publ. 08/20/2001.

Claims (5)

  1. A stand for calculating short-circuit currents of the inter-substation zone of an alternating current traction network, containing two traction substations A and B with transformer resistances ZtA and ZtB of voltage 110 / 27.5 (220 / 27.5) for two-way power supply to the traction network, which, when short-circuited ( KZ) represents the first three-beam star of resistances, two beams of which ZтcA and ZтcB are connected to the first terminals of the resistances of transformers ZтA and ZтB, the second terminals of which are connected to the first terminals of the equivalent resistances Z2 and Z3 of the supply lines 110 (220) kV traction x substations, and the third beam of the first three-ray star includes the equivalent resistance Z AB of the short circuit, characterized in that it is equipped with a power supply for the stand Uo and nodal mutual resistance Z1 of the supply lines 110 (220) kV of the second three-beam star of equivalent resistances Z1, Z2, Z3 , one output of the power supply is connected to the third beam of the short circuit with equivalent resistance Z AB of the first three-beam star of resistances, and the other output of the power supply is connected to the first output of the nodal mutual resistance Z1, the second output of which is connected to the connected second conclusions Z2 and Z3 of the supply lines 110 (220) kV, and the equivalent resistance Z1, Z2, Z3 are determined by the following mathematical expressions:
  2. Figure 00000015
  3. Figure 00000016
  4. Figure 00000017
  5. where Ik1 and Ik2 are the short-circuit currents of the inputs of transformers 110 (220) kV at short-circuit separately on each transformer of substations A and B; Ik1d and Ik2d - short-circuit currents of inputs of transformers 110 (220) kV at short-circuit simultaneously at the inputs of two indicated transformers.
RU2018146585A 2018-12-26 2018-12-26 Stand for calculation of short circuit currents of inter-substation zone of traction ac network RU2705517C1 (en)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SU1270778A1 (en) * 1984-01-11 1986-11-15 Новосибирский электротехнический институт Device for simulating transient short-circuit current
RU2011569C1 (en) * 1990-05-07 1994-04-30 Московский Институт Инженеров Железнодорожного Транспорта Device for physical modelling of power system of electric railroad
RU72915U1 (en) * 2007-12-20 2008-05-10 Государственное образовательное учреждение высшего профессионального образования "Дальневосточный государственный университет путей сообщения" (ДВГУПС) Test stand for current conducting elements of contact suspension
RU2397077C1 (en) * 2009-04-20 2010-08-20 Леонид Абрамович Герман Method of determining nodal mutual resistance of railway traction circuit
CN105044559A (en) * 2014-08-20 2015-11-11 上海交通大学 Transformer station grounding grid partitional fault diagnosis method

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SU1270778A1 (en) * 1984-01-11 1986-11-15 Новосибирский электротехнический институт Device for simulating transient short-circuit current
RU2011569C1 (en) * 1990-05-07 1994-04-30 Московский Институт Инженеров Железнодорожного Транспорта Device for physical modelling of power system of electric railroad
RU72915U1 (en) * 2007-12-20 2008-05-10 Государственное образовательное учреждение высшего профессионального образования "Дальневосточный государственный университет путей сообщения" (ДВГУПС) Test stand for current conducting elements of contact suspension
RU2397077C1 (en) * 2009-04-20 2010-08-20 Леонид Абрамович Герман Method of determining nodal mutual resistance of railway traction circuit
CN105044559A (en) * 2014-08-20 2015-11-11 上海交通大学 Transformer station grounding grid partitional fault diagnosis method

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