JPH0946934A - Hdlc telecommunication slave station for distribution substation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To transmit the three-phase unbalance rate and the occurrence of three-phase unbalance to a distributed transformation CPU system by taking in each-phase current of three-phase three-line system, and computing the three- phase unbalance rate. SOLUTION: Each-phase current of a three-phase three-line system of a circuit is taken in a digital converter 2, and a computing part 3 computes the three- phase unbalance rate from each-phase current value with, and a judging part 4 compares the three-phase unbalance rate with the set value to detect the occurrence of three-phase unbalance. A transmitter periodically telemeters the three-phase unbalance rate being computed at all times to an upper station, and when the judging part 4 detects the occurrence of the three-phase unbalance, this positionally transmits it to the upper station. Since the three-phase unbalance rate is computed from the three-phase current, the more accurate information can be obtained at all times than conventional one being so arranged as to grasp the three-phase unbalance situation from the magnitude of a zero-phase voltage by taking in the zero-phase voltage.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an H for a distribution substation.
DLC (High-level data link control procedure) Telecon (TC) Slave station with 3-phase unbalance detection function and 3-phase unbalance calculation function built-in .

[0002]

2. Description of the Related Art With regard to the acquisition of bank secondary current in a teleconverter slave station for a distribution substation, only the representative phase of three phases (red phase) has been acquired, but the number of telemeters has been greatly expanded with the adoption of HDLC transmission. All phases (black phase,
(Red phase, white phase) are captured. In this case, as shown in FIG. 6, the Y-connected CT (current transformer) neutral line (residual circuit) is commonly used for each phase current → I ₁ , → I ₂ , →.
I ₃ (→ indicates a vector) is incorporated in the set type digital converter 2.

Regarding detection of three-phase imbalance, FIG.
Constantly monitored by PT (potential transformer) set type digital converter 2 from an open delta T takes in the zero-phase voltage V ₀ which as shown in, when detecting a zero-phase voltage V ₀ that exceeds the set value , The peak value is held, the zero-phase voltage generation information and the demand value are transmitted to the logic section, and position transmission and telemeter transmission are performed to the upper station. In principle V
_{The 0} converter is built in the TC slave station. Further, the voltage between the black phase and the white phase is taken in as the bank secondary voltage.

[0004]

The above-mentioned conventional teleconverter slave station has the following problems.

(1) The teleconverter slave station takes in bank secondary currents for all phases, but it is ineffective because it is not used for detection of three-phase imbalance etc. just by taking in currents. ing.

(2) It is conceivable that currents of all phases are transmitted to the substation CPU system (distributed type system) and arithmetic processing is performed there to perform three-phase unbalance detection and three-phase unbalance rate calculation. Since the electric current is the required telemeter item in the standard specifications of the teleconverter slave station, it cannot be dealt with in this way (only the red-phase current is transmitted by the fixed-cycle telemeter item). Even if the currents of all the phases are transmitted by the fixed-cycle telemeter item, the load of the CPU system becomes heavy and the output of the display process becomes slow because of the extra calculation process.

(3) In the distributed system, the telecon slave station shares the items conventionally processed by the system side (editing of power source accident, editing of CB trip order, monitoring of A system recovery abnormality, etc.), and CPU There is a policy to reduce the load of to speed up the output of display processing. Adding new arithmetic processing to the CPU system goes against this policy.

(4) The main purpose of taking in the zero-phase voltage V ₀ is to grasp the value at the time of a ground fault, and it is difficult to grasp the three-phase unbalanced condition in normal times. It is not completely useless, but if it is sufficient to capture V ₀ for operation, it is not necessary to capture the bank secondary currents of all phases (at most, to the CRT screen of the substation CPU system or the measurement recording format). It is only used for display output).

(5) Some power converters have a built-in three-phase unbalance detection function (Japanese Patent Application No. 5-244207).
However, this three-phase unbalanced ejecting function is a three-phase four-wire system in which the current of the vector sum of each phase current flows into the neutral wire and the phase difference of each phase is always 120 °. Not applicable to expressions.

The present invention has been made in view of the above-mentioned conventional problems, and its object is to assume that the secondary circuit of the main transformer is a three-phase three-wire system. Three
To provide an HDLC teleconverter slave station for a distribution substation with a built-in three-phase unbalance detection function that calculates the phase unbalance rate and can transmit the three-phase unbalance rate and the three-phase unbalance rate generation to a higher station. It is in.

[0011]

In order to achieve the above object, an HDLC teleconverter slave station for distribution substation in the present invention takes in each phase current of a three-phase three-wire circuit and outputs each phase current value. An aggregate digital converter, an arithmetic unit that calculates a three-phase imbalance ratio from each phase current value, a comparison unit that compares the calculated three-phase imbalance ratio with a set value, and detects the occurrence of a three-phase imbalance. Position transmission means for transmitting a three-phase imbalance occurrence signal to the upper station when three-phase imbalance occurrence is detected, and fixed period telemeter transmission means for transmitting the calculated three-phase imbalance ratio to the upper station. Is characterized by.

The aggregate type digital converter takes in each phase current of the three-phase three-wire type distribution line and converts it into each phase current value.
The calculation unit calculates the three-phase unbalance rate from the current value of each phase.
The comparison unit compares the three-phase unbalance rate with a set value to detect the occurrence of three-phase unbalance. The position transmitting means transmits the signal to the upper station when the occurrence of three-phase imbalance is detected. The constant period telemeter transmission means transmits the calculated three-phase unbalance rate to the upper station at regular intervals. Since the unbalance of the three-phase three-wire type distribution line is calculated from each phase current and transmitted to the upper station without obtaining from the zero-phase voltage, the master station accurately grasps the normal three-phase unbalance situation. be able to.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the system configuration of a teleconverter slave station. The teleconverter slave station 1 is an aggregate type digital converter 2 to which the main transformer secondary side phase currents detected by CT are input.
And a calculation unit 3 for calculating a three-phase unbalance rate from the absolute value of the converted current, and a judgment for comparing the three-phase unbalance rate with a set allowable value and outputting a three-phase unbalance generation signal. Part 4
And a three-phase unbalance rate is transmitted to the upper station by a fixed-cycle telemeter and a three-phase unbalance occurrence is position-transmitted. In addition, in the figure, 7 indicates a main transformer secondary box of the reduction type substation equipment.

Next, the calculation of the three-phase unbalance rate ε performed by the arithmetic unit 3 will be described.

The black-phase, red-phase, and white-phase current vectors fetched from the CT into the converter 3 are represented by → I ₁ , → I ₂ → I ₃ (→ represents a vector). In addition, the current value (magnitude of the current vector) output from the conversion unit is expressed as | → I ₁ |, | → I ₂
|, | → I ₃ |.

(1) Calculation of current and phase difference of each phase Since the three-phase three-wire line has no neutral wire, the vector sum of the current of each phase becomes 0 (zero).

[0017]

[Equation 1]

If the three phases are in equilibrium, as shown in FIG.
→ I ₁ , → I ₂ , → I ₃ are all equal in size, and regarding the phase difference, → I ₁ is taken as a reference vector, →
I ₂ is delayed by (2/3) π, and → I ₃ is advanced by (2/3) π.

When three-phase unbalanced, as shown in FIG.
The magnitudes of I ₁ , → I ₂ , and → I ₃ and the phase difference are different from those in the balanced state.

The data fetched by the arithmetic unit are the current values | → I ₁ |, | → I ₂ |, | → I ₃ | of each phase converted by the conversion unit. Based on these data, the calculation unit calculates the phase difference by using → I ₁ as a reference vector.

Since the vector sum of the phase currents is 0 as in the equation (1), these current vectors form a triangle as shown in FIG. In FIG. 3,-(π-α) is the phase difference between → I ₁ and → I _2, and π-γ is the phase difference between → I ₁ and → I ₃ . Therefore, let α and γ be | → I ₁ |, | → I ₂ |,
It is calculated from | → I ₃ |.

From the cosine theorem in the triangle of FIG. 3, (2)
The equation holds.

[0023]

[Equation 2]

When α is calculated from the equation (2),

[0025]

(Equation 3)

[0026]

(Equation 4)

When γ is obtained by the same procedure,

[0028]

(Equation 5)

From the equation (5), when the phase difference between → I ₂ and → I ₃ is calculated using → I ₁ as the reference vector, the equation (6)
It becomes like the formula (7).

[0030]

(Equation 6)

[0031]

(Equation 7)

(2) Calculation of three-phase imbalance ratio → When I ₁ is used as a reference vector and complex display of → I ₂ and → I ₃ is performed, equations (8) to (10) are obtained.

[0033]

(Equation 8)

[0034]

[Equation 9]

[0035]

(Equation 10)

The positive-phase current → I _A, the reverse-phase current → I _B (11)
Equation (12) is defined.

[0037]

[Equation 11]

[0038]

(Equation 12)

In equations (11) and (12), a indicates a vector operator.

[0040]

(Equation 13)

[0041]

[Equation 14]

[0042]

(Equation 15)

From equation (11), the magnitude of → I _A and → I _A |
→ Calculate I _A |.

[0044]

(Equation 16)

[0045]

[Equation 17]

[0046] (12) → and I _B from the equation, → I the size of the _B |
→ Calculate I _B |.

[0047]

(Equation 18)

[0048]

[Equation 19]

Based on the above results, the three-phase imbalance ratio ε is calculated as (2
It is calculated by the formula 0).

[0050]

(Equation 20)

The judging section 4 constantly compares the three-phase unbalance rate ε calculated by the calculating section 3 with the set value, and outputs a three-phase unbalance generation signal to the transmitting section 5 when the set value is exceeded. When this signal is input, the transmission unit 5 transmits the position to the higher station.

Further, the transmission unit 5 transmits the three-phase unbalance rate ε from the calculation unit 3 to the upper station by the fixed period telemeter.

Next, a calculation example of the three-phase unbalance rate will be shown.

(1) The currents of black phase, red phase and white phase are 110 for each.
In the case of 0 (A) (at equilibrium) Substituting the numerical values into the equations (4) and (5) to obtain α and γ,

[0055]

(Equation 21)

Therefore, the phase difference between → I ₁ and → I ₂ is-(π-α) =-(2/3) π = -120 °, → I from the equation (6).
The phase difference between ₁ and → I ₃ is π−γ = π− (π /
3) = (2/3) π = 120 °.

→ With I ₁ as the reference vector, (8)
The complex representations of → I ₁ , → I ₂ , and → I ₃ are obtained from the equations, (9), and (10) as follows.

[0058]

(Equation 22)

From the above results, the vector diagram is as shown in FIG.

Positive phase current → I _A is

[0061]

(Equation 23)

Reversed phase current → I _B is

[0063]

(Equation 24)

Therefore, the unbalance rate ε is 0 from the equation (20).
It becomes [%].

(2) When the black-phase current is 1100 [A], the red-phase current is 1075 [A], and the white-phase current is 1050 [A], the unbalance rate is obtained by the same procedure as in (1).

From equations (4) and (5),

[0067]

(Equation 25)

→ I ₁ and → I ₂ phase difference − (180.00) −57.72) = − 122.28 ° → I ₁ and → I ₃ phase difference 180.00−59.95 = 120.05 ° → complex display of I ₁ , → I ₂ , → I ₃ → I ₁ = 1100∠0 = 1100e ^jo = 1100 → I ₂ ＝ 1075∠−122.28 ° = 1075e ^{-j122 ・ 28} ＝ 1075 × {cos122.28-jsin122.28} = -574.11- j908.86 → I 3 = 1050∠120.05 = 1050 × {cos120.05 + jsin120.05} = vector diagram than -525.79 + j908.87 above results Is as shown in FIG.

Positive phase current → I _A is

[0070]

(Equation 26)

[0071] reverse-phase current → I _B is,

[0072]

[Equation 27]

Therefore, the three-phase unbalance rate ε is 2.68 [%] from the equation (20). In the above embodiment, the current for one bank is fetched, but actually, the current for three banks is fetched and the calculation of the three-phase unbalance rate, the determination of the three-phase unbalance occurrence, and the transmission are performed for each bank.

The three-phase unbalanced detector can be applied to a power converter, an unbalanced detection relay, etc. as described below.

(1) Power converter After the current of each phase is taken in via CT, the above three-phase unbalance rate is calculated, and the value is output to the teleconverter or local operation panel as analog or digital output. .

(2) Unbalance detection relay After the current of each phase is taken in via CT, the above three-phase unbalance rate is calculated, and when it exceeds the set value, CB
The trip signal is output (the settling range is made more sensitive than these relays so that they operate before the open-phase relay or the ground fault protection relay).

(3) Incorporation into 3-phase active power converter and 3-phase reactive power converter The 3-phase active power converter and 3-phase reactive power converter are measured using the 2-power meter method. The prerequisite is that the phases are in equilibrium. Therefore, the three-phase unbalance detection function is incorporated in these converters to calculate the three-phase unbalance ratio, and if it exceeds the allowable value, external non-voltage contact output is performed, and the active power value and reactive power value are output externally. Lock the output.

[0078]

Since the present invention is configured as described above, it has the following effects.

(1) The three-phase imbalance ratio can be obtained from the currents of the respective phases of the three-phase three-wire type distribution line. Therefore, it becomes possible to immediately (in real time) and accurately grasp the three-phase unbalanced condition in normal times.

(2) When the three-phase unbalance rate exceeds the set value (allowable value), the position is transmitted to the distributed substation CPU system, so that the unbalance of the three-phase circuit becomes excessive on the system side. You can know immediately.

(3) By knowing that the three-phase imbalance has become excessive on the system side and taking measures against it, it is possible to restore the normal state before the open-phase relay or the ground fault protection relay operates. Therefore, it is possible to prevent the occurrence of a power failure due to the breaker trip due to the relay operation.

(4) Since the three-phase unbalance rate is transmitted to the distributed substation CPU system by the fixed period telemeter, its value can be always grasped on the system side.

(5) Distributed transformer CPU when zero-phase voltage is generated
In the system, it is possible to grasp the accident situation in detail by editing the message using the transmitted three-phase imbalance rate.

[Brief description of drawings]

FIG. 1 is a system configuration diagram of a teleconverter slave station according to an embodiment.

FIG. 2 is a vector diagram at the time of three-phase equilibrium.

FIG. 3 is a current vector diagram of a three-phase three-wire line.

FIG. 4 is a current vector diagram (1) from the result of the calculation example.

FIG. 5 is a current vector diagram (2) from the result of the calculation example.

FIG. 6 is an explanatory diagram of a form of taking in a bank secondary current.

FIG. 7 is an explanatory diagram of a zero-phase voltage acquisition form.

[Explanation of symbols]

 1 ... Tele-con (TC) slave station 2 ... Collective digital converter 3 ... Calculation part 4 ... Judgment part 5 ... Transmission part 6 ... PIO unit 7 ... Main transformer secondary box of reduction type substation equipment

Claims (1)

[Claims] 1. An aggregate type digital converter that takes in each phase current of a three-phase three-wire circuit and outputs each phase current value, and an arithmetic unit that calculates a three-phase unbalance ratio from each phase current value. A comparison unit that compares the calculated three-phase unbalance rate with a set value to detect the occurrence of three-phase unbalance, and a position transmission unit that transmits a three-phase unbalance occurrence signal to the host station when three-phase unbalance occurrence is detected. An HDLC teleconverter slave station for a distribution substation, comprising: a constant period telemeter transmission means for transmitting the calculated three-phase unbalance rate to a host station.