KR20240021619A - Substation Integrated Protection System and Substation Integrated Monitoring Method - Google Patents

Abstract

The substation integrated protection system of the present invention includes a transformer of a substation, distribution busbars, a pi busbar connecting the distribution busbars, and at least three or more CTs installed on transmission lines that supply power to the distribution busbars; A monitoring unit that monitors the current of each part of the line responsible for the substation and checks whether a failure has occurred; and a failure determination unit that, when a failure occurs, calculates a bus ratio differential current with respect to the current values of the CTs, and determines whether the bus bar is broken from the calculated bus ratio differential current.

Description

Substation Integrated Protection System and Substation Integrated Monitoring Method}

The present invention is an all-in-one protection system that can determine in detail failures in the distribution and transmission lines in charge of a substation, and is an algorithm that protects the existing protection relays installed for each facility into one integrated system. It relates to the applied substation integrated protection system and substation integrated monitoring method.

To protect the substation facilities, a protective relay had to be installed for each facility. With the recent development of communication equipment and unification of communication standards (ex.IEC61850), it has become possible to simultaneously transmit current information generated in the event of a failure.

Figure 1 is a conceptual diagram of the installation of a protection relay in an existing substation.

Conventional substation protection/monitoring technology requires the installation of a protection relay for each facility, resulting in the cost of installing cables between the protection facility and the protection relay, and the cost and facility costs of connecting multiple facilities (transmission line protection, transformer protection, bus protection relay). Complexity has increased.

Republic of Korea Registered Publication No. 10-2259667

The present invention seeks to provide a substation integrated protection system and a substation integrated monitoring method that can quickly and accurately identify failures occurring in the substation.

The present invention seeks to provide a substation integrated protection system and a substation integrated monitoring method that can reduce construction costs required for cable installation between protection equipment and protection relays.

A substation integrated protection system according to an aspect of the present invention includes a transformer of a substation, distribution busbars, a pi busbar connecting the distribution busbars, and at least three installed on transmission lines that supply power to the distribution busbars. CTs above; A monitoring unit that monitors the current of each part of the line responsible for the substation and checks whether a failure has occurred; and a failure determination unit that, when a failure occurs, calculates a bus ratio differential current with respect to the current values of the CTs, and determines whether the bus bar is broken from the calculated bus ratio differential current.

Here, the failure determination unit may calculate the transformer ratio differential current with respect to the current values of CTs installed on both sides of the transformer, and determine whether the busbar is broken from the calculated transformer ratio differential current.

Here, the failure determination unit can determine which of the transmission lines has the maximum current and determine whether the transmission line is broken based on impedance calculated from the current value and voltage value of the transmission line with the maximum current.

Here, each of the CTs constitutes a transformer of a substation, distribution busbars, a pi busbar connecting the distribution busbars, and an overcurrent relay or ratio differential relay installed on transmission lines that supply power to the distribution busbars. It could be CT.

Here, the failure determination unit uses the operating current calculated as the vector sum of each current value as the numerator and the suppression current calculated as the scalar sum of the respective current values as the denominator for the current values of the at least three CTs. The bus ratio differential current can be calculated.

Here, when calculating the bus ratio differential current of each of the three phases, the same suppression current reflected as the maximum value among the three phases can be applied.

A substation integrated monitoring method according to another aspect of the present invention includes the steps of checking whether a failure has occurred while monitoring the current of each part of the line responsible for the substation; When a fault occurs, acquiring current values of each part of each monitored line; Calculate the bus ratio differential current for the current values of the CTs installed in the transformer of the substation, the distribution busbars, the pi busbar connecting the distribution busbars, and the transmission lines that supply power to the distribution busbars. determining whether the bus bar is broken from the bus bar ratio differential current; Calculating a transformer ratio differential current with respect to current values of CTs installed on both sides of the transformer, and determining whether a busbar is broken from the calculated transformer ratio differential current; Confirming which of the transmission lines has the maximum current; And it may include determining whether the transmission line is broken using impedance calculated from the current value and voltage value of the transmission line with the maximum current.

Here, in the step of checking whether a failure has occurred, if the bus voltage of the bus bar is less than a predetermined ratio compared to the rated voltage, it can be determined that a failure has occurred.

Here, in the step of determining whether the bus bar is broken from the bus ratio differential current, for the current values of at least three CTs, the operating current calculated as the vector sum of each current value is used as the numerator, and the scalar sum of each current value is used. The ratio differential current can be calculated using the suppression current calculated as the denominator.

Here, when calculating the ratio differential current of each of the three phases, the same suppression current reflected as the maximum value among the three phases can be applied.

Here, in the step of determining whether the transmission line is broken, the current value of the transmission line side CT provided in the breaker connecting the transmission line and the busbar is inversely converted and reflected as the current value of the transmission line of the maximum current. You can.

Implementing the substation integrated protection system and/or substation integrated monitoring method according to the spirit of the present invention of the above-described configuration has the advantage of quickly and accurately identifying failures occurring in the substation.

In addition, when the preliminary protection IED is applied through the proposal of the present invention, it is processed by one system, so the operator does not need to check multiple facilities in the event of a breakdown, thereby shortening the breakdown time and improving operational efficiency.

The substation integrated protection system and/or substation integrated monitoring method of the present invention has the advantage of reducing construction costs required for cable installation between protection equipment and protection relays.

From an economic perspective, assuming that the substation facility consists of three transmission lines, a busbar, and one transformer, the cost of installing a protection relay is approximately KRW 320 million (KRW 40 million/unit × 8 units = KRW 320 million). , When installing this design product, an 87.5% savings can be achieved at around 40 million won (installation cost for one unit).

In addition, in the case of the existing method, several protective relays must be set each time a new facility is expanded or the system is changed, while the designed method requires setting only one, which can increase work efficiency.

In addition, by replacing CTs for protecting existing transmission lines with CTs for busbar protection, the quantity of CTs can be reduced, thereby reducing costs.

The substation integrated protection system and/or substation integrated monitoring method of the present invention can be installed in software (digital twin), so it can be applied to the SA substation upper system, and has the advantage of contributing to the activation of digital substation construction policies in the future. .

Figure 1 is a conceptual diagram of the installation of a protection relay in an existing substation.
Figure 2 is a conceptual diagram of the installation of a protection system in a substation according to the spirit of the present invention.
Figure 3 is a block diagram showing an embodiment of a substation integrated protection system according to the spirit of the present invention.
Figure 4 is a line configuration diagram showing the protection section for each substation facility in which the substation integrated protection system of Figure 3 is involved.
Figure 5 is a flowchart showing an embodiment of a substation integrated monitoring method performed by the substation integrated protection system according to the idea of the present invention for the protection section for each substation facility in Figure 4.
Figure 6 is a circuit diagram showing the operation structure of a general ratio differential protection relay.

In describing the present invention, terms such as first and second may be used to describe various components, but the components may not be limited by the terms. Terms are intended only to distinguish one component from another. For example, a first component may be referred to as a second component, and similarly, the second component may be referred to as a first component without departing from the scope of the present invention.

When a component is mentioned as being connected or connected to another component, it can be understood that it may be directly connected to or connected to the other component, but other components may exist in between. .

The terms used herein are only used to describe specific embodiments and are not intended to limit the invention. Singular expressions may include plural expressions, unless the context clearly indicates otherwise.

In this specification, terms such as include or have are intended to designate the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, including one or more other features or numbers, It can be understood that the existence or addition possibility of steps, operations, components, parts, or combinations thereof is not excluded in advance.

Additionally, the shapes and sizes of elements in the drawings may be exaggerated for clearer explanation.

Figure 2 is a conceptual diagram of the installation of a protection system in a substation according to the spirit of the present invention.

The present invention proposes a substation integrated protection system and a substation integrated monitoring method in which each CT trigger structure of various existing protection relays centrally monitors the function of individually monitoring the corresponding point and operates the corresponding relay centrally. In other words, a plan has been prepared to transition from using protection relays for each transmission line, busbar, and transformer to an integrated protection system.

Figure 3 is a block diagram showing an embodiment of a substation integrated protection system according to the spirit of the present invention.

The substation integrated protection system shown includes a transformer of a substation, distribution busbars, a pi busbar connecting the distribution busbars, and at least three CTs installed on transmission lines that supply power to the distribution busbars; A monitoring unit 120 that monitors the current of each part of the line responsible for the substation and checks whether a failure has occurred; And when a failure occurs, it may include a failure determination unit 140 that calculates the bus ratio differential current with respect to the current values of the CTs and determines whether the bus bar is broken from the calculated bus ratio differential current.

The fault determination using the busbar ratio differential current performed by the failure determination unit 140 is a conventional ratio differential relay (a relay for transformer protection, etc.) that determines the vector difference between the current flowing into the protection section and the current flowing out, Faults can be recognized more precisely and accurately than in the case of the ratio differential current method (relay that operates at the ratio of current). In other words, it has the advantage of being able to identify busbar failures that do not trigger (operate) with the 2CT current difference provided by the existing ratio differential relay.

In addition, the failure determination unit 140 calculates the transformer ratio differential current with respect to the current values of the CTs installed on both sides of the transformer, and determines whether the busbar is broken from the calculated transformer ratio differential current and/or the transmission line. Among the furnaces, it is possible to confirm which one has the maximum current, and to additionally determine whether the transmission line is broken using impedance calculated from the current and voltage values of the transmission line with the maximum current.

The monitoring unit 120 and the failure determination unit 140 may form one substation integrated protection device 100 that is physically independent from the CTs. As a means of performing data processing, the substation integrated protection device 100 includes information on the occurrence of a fault in the line responsible for the substation or information on the basis for determining whether a fault has occurred, current measurement values or waveform information of the CTs, and PT installed on the line in charge of the substation. A storage unit 160 for storing voltage measurement values or waveform information and/or outputs failure occurrence information and specific failure information (whether a busbar, transformer, or transmission line is broken) according to the present invention for the manager of the substation ( display) and may further include a user interface (UI) 180 that receives action instructions for circuit breakers, etc.

The lines of the transformer, the distribution busbars, the pi busbars connecting the distribution busbars, and the transmission lines that supply power to the distribution busbars can be collectively referred to as substation lines.

When the fault determination unit 140 calculates the bus ratio differential current, the current measurement values of at least three CTs on the line responsible for the substation are required, preferably one from the transformer line and each from the distribution bus lines. One current measurement value is applied, one from the pi busbar connecting the distribution busbars, and one current measurement value from each of the transmission lines that supply power to the distribution busbars.

Each of the above CTs may be a CT installed separately at corresponding points of the line responsible for the substation in order to build a central integrated protection system according to the spirit of the present invention, but in this case, there is a disadvantage in that the construction cost and construction work are large. .

When attempting to build a centrally integrated protection system according to the spirit of the present invention from an economical point of view, each of the CTs is connected to a transformer of a substation, distribution busbars, a pi busbar connecting the distribution busbars, and the distribution busbars. It is advantageous to use a CT that constitutes an overcurrent relay or ratio differential relay installed on transmission lines that supply power.

Specifically, by maintaining the ratio differential relay and overcurrent relay configuration of the existing 2CT, each switch performs monitoring and switching according to the model type, without adding a separate measuring device, and each existing relay can be used as a trigger. Using the measured values of the equipped CTs, an economical and efficient all-in-one protection system can be built.

In other words, hardware costs are reduced by adding an algorithm to use the existing bus bar protection CT overlapping with the transmission line protection CT, and in particular, the transmission line protection CT (current transformer for instrumentation) that changes the direction of the bus bar protection relay. By using it, the amount of CT and cable can be reduced.

In this case, while providing an integrated protection function for the substation according to the spirit of the present invention, it is possible to use the protection function based on each existing protection relay as a backup.

Figure 4 is a line configuration diagram showing the protection section for each substation facility in which the substation integrated protection system of Figure 3 is involved.

As shown in Figure 4, protection devices (IEDs) are used for each facility section (transformer protection, transmission line protection, bus bar protection), and in the case of the SA substation, current and voltage information in the event of a failure is transmitted to the upper system in accordance with the IEC61850 standard. This is possible.

FIG. 5 is a flowchart illustrating an embodiment of a substation integrated monitoring method performed by the substation integrated protection system according to the idea of the present invention for the protection section for each substation facility in FIG. 4.

The substation integrated monitoring method shown includes the steps of monitoring the current of each part of the line responsible for the substation (S120) and checking whether a failure has occurred (S140); When a failure occurs, obtaining current values of each part of each monitored line (S160);

Calculate the bus ratio differential current for the current values of the CTs installed in the transformer of the substation, the distribution busbars, the pi busbar connecting the distribution busbars, and the transmission lines that supply power to the distribution busbars (S220 ), determining whether the bus bar is broken from the calculated bus ratio differential current (S240); Calculating the transformer ratio differential current with respect to the current values of the CTs installed on both sides of the transformer (S260), and determining whether the busbar is broken from the calculated transformer ratio differential current (S280). Calculating the maximum current among the transmission lines Confirming what you have (S320); And it may include a step (S342 to S346 or S352 to S356) of determining whether the transmission line is broken using impedance calculated from the current value and voltage value of the transmission line with the maximum current.

In the step of checking whether a failure has occurred (S140), if the bus voltage of the bus is less than a predetermined ratio compared to the rated voltage, it is determined that a failure has occurred. In other implementations, different standards are applied, or a protective relay installed on the line in charge of the substation is used. It can be performed by applying a blocking signal or receiving a failure determination from a higher level server.

Figure 5 shows an algorithm that acquires each current data and distinguishes failure sections for each facility. The case in Figure 4 will be examined sequentially.

First, when the voltage of the 1st and 2nd busbars (Nos. 11 and 12) in FIG. 4 falls below 80%, this is recognized as a failure (S140), and a signal is generated to store the current in each IED and send the current to the upper system ( S160). At this time, the ratio is calculated using the precise ratio differential calculation formula (i.e., bus ratio differential current) proposed in the present invention for the acquired current of the bus bar, and if the ratio is more than 40%, it is determined that the bus bar is broken (S220 ~ S250) ).

If it is less than 40% in step S240, the ratio is calculated using the precise ratio differential calculation formula (i.e., transformer ratio differential current) designed using the transformer side acquired current data (No. 7.8) (S260). At this time, if it is more than 40%, it can be determined that the transformer has failed (S290).

Here, if it is less than 40%, the maximum current flowing in the transmission line is assumed to be a fault, and the bus current data on the transmission line side is inverted to calculate the impedance to determine the fault location (S342 ~ S346 or S352 ~ S356).

Accordingly, in the step of determining whether the transmission line of FIG. 5 is broken (S342 to S346 or S352 to S356), as the current value of the transmission line of the maximum current, the circuit breaker (CB) connecting the transmission line and the bus bar The current value of the CT on the transmission line side provided in is inversely converted and reflected.

Before detailing the fault determination process using the bus ratio differential current performed in S220 to S250 according to the spirit of the present invention, we will look at the ratio differential calculation process of a general ratio differential protection relay.

Figure 6 is a circuit diagram showing the operation structure of a general ratio differential protection relay.

Ratio differential protection relays are generally widely installed on transformers. Figure 6 illustrates the installation structure for transformers. In the case of substation-side lines to which the present invention is applied, they can be installed not only on transformers but also on circuit breakers (CB). there is.

In the case of the existing ratio differential relay operation formula of FIG. 6, it can be calculated according to Equation 1 below using the ratio of the operating current and the suppression current.

In Equation 1 above, the operating current is calculated by calculating the vector sum of the currents of each phase, and the suppression current is calculated by calculating the scalar sum of the currents of each phase.

However, because the phase current is used, the operation error value due to the zero-phase current always exists.

On the other hand, in the case of failure determination using the bus ratio differential current according to S220 to S250 in the present invention, the zero phase current, which can be a cause of error that may occur when calculating the ratio differential current, is excluded from the operating current formula and the suppression current is calculated. Precision in fault detection can be increased by calculating based on the maximum current value.

In other words, failure determination (S220 to S250) using the bus bar ratio differential current can identify a bus bar failure to a degree that does not trigger (operate) with the current difference of 2CT provided by the existing ratio differential relay.

Specifically, as a precision ratio differential current calculation formula used to calculate failure determination (S220 ~ S250) using the bus ratio differential current, the bus ratio differential current is calculated using the existing lump compensation method (compute video portions collectively and apply to all). ), unlike the current itself, zero-sequence compensation is applied as an instantaneous value (only the normal and negative-sequence are used, and the zero-sequence current is deleted when calculating the current), and when calculating the suppression current, unlike the existing scalar sum, the normal and negative-sequence current for each phase is applied as an instantaneous value. In terms of applying the maximum value, precision increases compared to before.

The mathematical expressions for this are sequentially detailed below.

When there are two CTs, the calculation formula for the busbar and transformer is as follows.

- CT1: A, B, C phase positive sequence current (IAN111, IBN111, ICN111), negative sequence current (IAN121, IBN121, ICN121)

- CT2: A, B, C phase positive sequence current (IAN212, IBN212, ICN212), negative sequence current (IAN222, IBN222, ICN222)

At this time, the operating current of each phase can be obtained according to Equation 2 below.

Additionally, the suppression current calculation equation may follow Equation 3 below.

In Equation 3 above, it can be seen that when calculating the ratio differential current of each phase of the three phases, the same suppression current reflected as the maximum value among the three phases is applied to all three phases.

To summarize the contents related to the above-mentioned equations, in the steps (S220, S240) of determining whether the bus bar is broken from the bus bar ratio differential current, the vector sum of each current value for the current values of at least three or more CTs The ratio differential current is calculated using the operating current calculated as the numerator and the suppression current calculated as the scalar sum of each current value as the denominator. In addition, when calculating the ratio differential current of each of the three phases, the same suppression current reflected as the maximum value among the three phases is applied.

Therefore, the ratio differential calculation equation for calculating the bus ratio differential current proposed in the present invention can be expressed as operating current/suppression current as shown in Equation 4 below.

Depending on implementation, the transformer ratio differential current applied in step S260 of FIG. 5 may also be calculated according to Equation 4 above.

Next, in order to examine the effect of the present invention, we will compare the results when calculating with the designed method with the results when calculating with an existing general ratio differential relay.

Table 1 below summarizes cases of internal failure in the primary winding, and Table 2 summarizes cases of internal failure in the secondary winding.

The failure cases in Tables 1 and 2 above are the results of simulating internal failures in the primary and secondary windings, which are the most difficult to distinguish between phases in the event of a failure in a ratio differential relay. It can be seen that, except for the 5% to 30% indeterminable range, phase A, which is a malfunction, is accurately classified compared to the existing method.

Those skilled in the art to which the present invention pertains should understand that the present invention can be implemented in other specific forms without changing its technical idea or essential features, and that the embodiments described above are illustrative in all respects and not restrictive. Just do it. The scope of the present invention is indicated by the claims described later rather than the detailed description, and all changes or modified forms derived from the meaning and scope of the claims and their equivalent concepts should be construed as being included in the scope of the present invention. .

100: Substation integrated protection device
120: monitoring unit
140: failure determination unit
160: storage unit
180: User Interface (UI)

Claims (11)

A transformer of a substation, distribution busbars, a pi busbar connecting the distribution busbars, and at least three CTs installed on transmission lines that supply power to the distribution busbars;
A monitoring unit that monitors the current of each part of the line responsible for the substation and checks whether a failure has occurred; and
When a failure occurs, a failure determination unit calculates the bus ratio differential current for the current values of the CTs and determines whether the bus bar is broken from the calculated bus ratio differential current.
Substation integrated protection system including.
According to paragraph 1,
The failure determination unit,
A substation integrated protection system that calculates the transformer ratio differential current with respect to the current values of the CTs installed on both sides of the transformer and determines whether the busbar is broken from the calculated transformer ratio differential current.
According to paragraph 1,
The failure determination unit,
A substation integrated protection system that confirms which of the transmission lines has the maximum current and determines whether the transmission line is broken based on impedance calculated from the current value and voltage value of the transmission line with the maximum current.
According to paragraph 1,
Each of the above CTs is,
A substation integrated protection system that is a CT that consists of a transformer of the substation, distribution busbars, a pi busbar connecting the distribution busbars, and an overcurrent relay or ratio differential relay installed on transmission lines that supply power to the distribution busbars.
According to paragraph 1,
The failure determination unit,
For the current values of the at least three CTs, the bus ratio differential current is calculated using the operating current calculated as the vector sum of each current value as the numerator and the suppression current calculated as the scalar sum of each current value as the denominator. A substation integrated protection system.
According to clause 5,
A substation integrated protection system that applies the same suppression current reflected as the maximum value among the three phases when calculating the bus ratio differential current of each phase of the three phases.
Monitoring the current of each part of the line responsible for the substation and checking whether a failure has occurred;
When a fault occurs, acquiring current values of each part of each monitored line;
Calculate the bus ratio differential current for the current values of the CTs installed in the transformer of the substation, the distribution busbars, the pi busbar connecting the distribution busbars, and the transmission lines that supply power to the distribution busbars. determining whether the bus bar is broken from the bus bar ratio differential current;
Calculating a transformer ratio differential current with respect to current values of CTs installed on both sides of the transformer, and determining whether a busbar is broken from the calculated transformer ratio differential current;
Confirming which of the transmission lines has the maximum current; and
A step of determining whether the transmission line is broken using impedance calculated from the current value and voltage value of the transmission line with the maximum current.
Substation integrated monitoring method including.
In clause 7,
In the step of checking whether the above failure has occurred,
A substation integrated monitoring method that determines that a failure has occurred if the bus voltage of the bus is less than a predetermined ratio compared to the rated voltage.
In clause 7,
In the step of determining whether the bus bar is broken from the bus ratio differential current,
For current values of at least three CTs,
A substation integrated monitoring method that calculates the ratio differential current using the operating current calculated as the vector sum of each current value as the numerator and the suppression current calculated as the scalar sum of each current value as the denominator.
According to clause 9,
A substation integrated monitoring method that applies the same suppression current reflected as the maximum value among the three phases when calculating the ratio differential current of each phase of the three phases.
In clause 7,
In the step of determining whether the transmission line is broken,
A substation integrated monitoring method that inversely converts and reflects the current value of the transmission line-side CT provided in a breaker connecting the transmission line and the busbar as the current value of the transmission line of the maximum current.

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