RU2705517C1  Stand for calculation of short circuit currents of intersubstation zone of traction ac network  Google Patents
Stand for calculation of short circuit currents of intersubstation zone of traction ac network Download PDFInfo
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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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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 intersubstation section of traction AC network with twoway 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 threebeam 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 shortcircuit currents of feed lines of the overhead system, namely, obtaining accurate values of shortcircuit currents of supply lines of traction substations and sectioning stations, which are necessary for highquality 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 intersubstation zone with twoway power supply.
"Prior art"
In [1], a physical model of the electric railway was proposed, which makes it possible to determine shortcircuit 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 intersubstation zone with two traction substations is proposed for the formation of twoway power supply to the traction network. In it, the resistance of the traction substation is represented by the sum of the resistances of the stepdown 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 shortcircuit 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 shortcircuit 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 shortcircuit currents for any sections at given shortcircuit 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 intersubstation 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 twoway power supply of the traction network, which, when shortcircuited, represents the first threebeam 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 threeray 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 twoway power supply, i.e. shortcircuit 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 shortcircuit currents in the traction network  27%. Typically, the error with increasing distance from the power source can reach 3040%. 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 shortcircuit 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 threebeam 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 shortcircuit power at the inputs to the substation:
where S _{cA} and S _{cB} are the shortcircuit 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 shortcircuit capacities at the inputs of 110 (220) kV substations or shortcircuit currents or input resistances. Additionally, the power system should give one more parameter: shortcircuit power (shortcircuit currents or input resistance) with simultaneous shortcircuit 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)
where  Ik1 and Ik2  shortcircuit currents of transformer inputs 110 (220) kV at shortcircuit separately at each transformer of substations A and B; Ik1d and Ik2d  shortcircuit currents of inputs of transformers 110 (220) kV at shortcircuit simultaneously at the inputs of two indicated transformers.
To achieve the above objectives of the invention proposed:
A stand for calculating shortcircuit currents of the intersubstation 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 twoway power supply to the traction network, which, when shortcircuited ( KZ) represents the first threebeam 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 threeray 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 threebeam 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 threebeam 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:
where  Ik1 and Ik2  shortcircuit currents of transformer inputs 110 (220) kV at shortcircuit separately at each transformer of substations A and B; Ik1d and Ik2d  shortcircuit currents of inputs of transformers 110 (220) kV at shortcircuit 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 highquality 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: shortcircuit experience at the injection of a TPA transformer;
In FIG. 3: shortcircuit experience at the input of the TPV transformer;
In FIG. 4: shortcircuit 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 stepdown 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 shortcircuit 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 shortcircuit 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 shortcircuit currents at the stand is a working tool for determining shortcircuit 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 shortcircuit currents when the traction substation is switched on after its installation.
Examples:
For three shortcircuit experiments, threephase shortcircuit diagrams are presented at the bushings of traction substation transformers:
 FIG. 2: shortcircuit experience at the injection of a TPA transformer;
 FIG. 3: shortcircuit experience at the input of the TPV transformer;
 FIG. 4: shortcircuit 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
where Ik1 and Ik2  shortcircuit currents of inputs at shortcircuit separately on each transformer A and B;
Ik1d and Ik2d  shortcircuit currents of inputs at shortcircuit simultaneously at the inputs of two transformers.
Solving the equations together, we define
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 07.021.42015 “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. 1621.
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)
 A stand for calculating shortcircuit currents of the intersubstation 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 twoway power supply to the traction network, which, when shortcircuited ( KZ) represents the first threebeam 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 threeray 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 threebeam 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 threebeam 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:
 where Ik1 and Ik2 are the shortcircuit currents of the inputs of transformers 110 (220) kV at shortcircuit separately on each transformer of substations A and B; Ik1d and Ik2d  shortcircuit currents of inputs of transformers 110 (220) kV at shortcircuit simultaneously at the inputs of two indicated transformers.
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Citations (5)
Publication number  Priority date  Publication date  Assignee  Title 

SU1270778A1 (en) *  19840111  19861115  Новосибирский электротехнический институт  Device for simulating transient shortcircuit current 
RU2011569C1 (en) *  19900507  19940430  Московский Институт Инженеров Железнодорожного Транспорта  Device for physical modelling of power system of electric railroad 
RU72915U1 (en) *  20071220  20080510  Государственное образовательное учреждение высшего профессионального образования "Дальневосточный государственный университет путей сообщения" (ДВГУПС)  Test stand for current conducting elements of contact suspension 
RU2397077C1 (en) *  20090420  20100820  Леонид Абрамович Герман  Method of determining nodal mutual resistance of railway traction circuit 
CN105044559A (en) *  20140820  20151111  上海交通大学  Transformer station grounding grid partitional fault diagnosis method 

2018
 20181226 RU RU2018146585A patent/RU2705517C1/en active
Patent Citations (5)
Publication number  Priority date  Publication date  Assignee  Title 

SU1270778A1 (en) *  19840111  19861115  Новосибирский электротехнический институт  Device for simulating transient shortcircuit current 
RU2011569C1 (en) *  19900507  19940430  Московский Институт Инженеров Железнодорожного Транспорта  Device for physical modelling of power system of electric railroad 
RU72915U1 (en) *  20071220  20080510  Государственное образовательное учреждение высшего профессионального образования "Дальневосточный государственный университет путей сообщения" (ДВГУПС)  Test stand for current conducting elements of contact suspension 
RU2397077C1 (en) *  20090420  20100820  Леонид Абрамович Герман  Method of determining nodal mutual resistance of railway traction circuit 
CN105044559A (en) *  20140820  20151111  上海交通大学  Transformer station grounding grid partitional fault diagnosis method 
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