JP2597721B2 - Protection device for DC power circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a DC power supply circuit for transmitting an electric power from a DC bus to a power supply line via a circuit breaker to operate an electric vehicle, and particularly a small-scale power supply circuit. The present invention relates to a protection device for a DC power supply circuit that can reliably perform protection in an accident.

(Prior Art) In general, in electric railways, the power for powering electric vehicles is generally transmitted to a power line by direct current except for the Shinkansen and a part of the AC section. On the other hand, the protection of this DC power cable is, for example, because there is no parameter such as frequency and phase because it is direct current, and because the load is an electric car, it fluctuates and moves. The protection scheme must be limited. One of the most prominent and commonly used protection methods among the limited protection methods is the ΔI relay method.

Hereinafter, this ΔI relay system will be described with reference to FIGS. 3 to 5.

FIG. 3 is a diagram showing an example of a general system configuration when a ΔI relay system is applied to a DC power supply circuit in an electric railway. In FIG. 3, the electric car EL is driven by electric power transmitted from the DC buses AL1 and AL2 to the power line K via the disconnectors DS1 and DS2, the high-speed circuit breakers HSCB1 and HSCB2, and the cable heads CH1 and CH2. Is performed. On the other hand, ΔI relays DYR1 and DYR2 are installed to protect the feeder K from accidents.
ΔI relays DYR1 and DYR2 by the CT secondary current detected in 2
The high-speed circuit breakers HSCB1 and HSCB
2 is cut off, and the electric wire K in the accident section is disconnected from the system.

In the electric vehicle load, a large current flows in a short time due to notch operation or the like, and the amount of the current fluctuates greatly. Therefore, if only the overcurrent element of the high-speed circuit breaker is used for these protections, the possibility of erroneous operation to these loads increases, so the sensitivity setting of the overcurrent element must be lowered, and the actual fault area current Will not work. Therefore, there is a ΔI relay method as a protection method effective in these accident areas.
In this ΔI relay system, the amount of change (Δ
I amount), the ΔI amount (change amount of current per unit time) of the relay is set based on the ΔI amount generated by the load current as shown in FIG. In addition, the detection protection is performed only in the event of an accident by increasing the size.

FIG. 5 is a block diagram showing a specific configuration example of a ΔI relay conventionally used. In FIG.
The ΔI current transformer DCT1 generates a CT secondary current corresponding to the amount of change per hour (ΔI amount) of the DC current flowing in the DC power circuit (main circuit), and generates a CT secondary current proportional to the ΔI amount. The current is input to the ΔI relay DYR1. In the ΔI relay DYR1, the input current is converted into a logic-level signal by the input converter IC1, and the signal is converted into the signal Δ by the set value setter SET1.
Comparing the I amount setting value with the comparator OP1, when the ΔI amount from the input converter IC1 is larger, the comparator OP1 operates to drive the relay operation signal amplifier AMR1 and trip the high speed circuit breaker HSCB1. To protect the cable K.

By the way, the electric load of the electric railway is affected by the number of electric cars passing through the electric wire K, the composition, the electric car performance, or the time zone, the number of electric cars, and the like, so that the load fluctuation is severe and complicated. I have to be. The ΔI relay system is a relay system used for distinguishing these load currents and fault currents. However, in order to detect a small-scale arc fault and other faults, the sensitivity of the ΔI relay is used. The setting value must be increased, but if the sensitivity setting value is increased too much, it will malfunction due to actual load fluctuation, so when humans set the relay, in order to prevent malfunction due to sufficient load fluctuation, There is a tendency to set too low a sensitivity setting value. This is because the setting of the maximum ΔI amount due to the load relies on desk calculation or human experience, and therefore the maximum ΔI amount due to a complicated load variation pattern cannot be accurately grasped. For this reason, if the sensitivity setting value of the relay is lowered as necessary, an unprotected area in protection coordination that cannot be detected in the event of an actual accident increases, which is not preferable in system operation.

(Problems to be Solved by the Invention) As described above, in the related art, since the sensitivity setting value has been determined by humans by calculation or experience, the sensitivity setting according to the actual load condition of the cable cannot be performed. There was a problem that it was not possible to provide protection in the event of a small-scale accident of the electric wire.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a highly reliable DC power circuit protection device capable of maximizing the sensitivity setting value and reliably protecting a power cable in a small-scale accident.

[Means for Solving the Problems] In order to solve the above-mentioned problems, in the protection device for a DC power circuit of the present invention, a change ΔI per hour of a DC current flowing through the DC power circuit is provided. And a maximum value storage means for inputting the change amount ΔI detected by the current change amount detection means and storing a maximum value of the change amount ΔI due to a load change of the DC power supply circuit up to the present time. A setting value calculating unit that calculates and outputs a sensitivity setting value in consideration of a predetermined margin to the maximum value detected by the maximum value storage unit, and a setting value setting unit that outputs a preset sensitivity setting value. A setting value selecting means for selecting and outputting one of the sensitivity setting value output from the setting value calculating means and the sensitivity setting value output from the setting value setting means, and a change from the current change amount detecting means. Quantity ΔI and settling The sensitivity setting value is compared with the sensitivity setting value from the value selection means, and when it is determined that the variation ΔI is greater than the sensitivity setting value, the comparison means for outputting a strip command to the circuit breaker and the comparison means determine that the sensitivity setting value is greater than the sensitivity setting value. Input inhibiting means for inhibiting input of the change amount ΔI from the current change amount detecting means to the maximum value storage means.

(Operation) Therefore, in the DC power circuit protection device of the present invention, the maximum value of the variation ΔI due to the actual load fluctuation of the power cable up to the present time is stored, and a value obtained by adding a margin to this maximum value is stored. Is automatically set as a sensitivity setting value, it is possible to perform sensitivity setting according to the actual load condition of the cable.

Further, the set value selection means determines whether the change ΔI detected by the current change detection means is caused by a load change or an accident, for example, by using a sensitivity set value preset by the operator. ing. Therefore, it is possible to prevent the change amount ΔI from being determined with an abnormally low sensitivity set value at the initial operation of the apparatus.

In addition, since the change amount ΔI caused by the load change is prohibited from being used in the calculation as the sensitivity setting value, the reliability of the sensitivity setting value automatically calculated is improved.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing a protection device for a DC power circuit according to the present invention, Δ.
5 is a block diagram showing a configuration example of an I relay, and the same elements as those in FIG. 5 are denoted by the same reference numerals. As shown in FIG. 1, the ΔI relay according to the present embodiment includes a ΔI current transformer DCT1 as a current change amount detecting means and a ΔI relay main body DYR3.
The ΔI relay body DYR3 includes an input converter IC1, a switch SW1, a maximum value memory unit MME, a calculator CAL, a set value manual setting device SSET, a selection switch COS, and a set value memory unit NSET. Comparator OP1 and relay operation signal amplifier AMR
1 and a set value display DS.

Here, the ΔI current transformer DCT1 is a DC power circuit (main circuit).
CT that matches the amount of change in DC current per hour ΔI
A secondary current is generated, and a CT secondary current proportional to the amount of change ΔI is input to the ΔI relay body DYR3. On the other hand, ΔI
In the relay body DYR3, the input converter IC1 converts a CT secondary current from the ΔI current transformer DCT1 into a signal of a logic level. The switch SW1 is for selecting whether or not to input an output signal from the input converter IC1 to the maximum value memory unit MME. The maximum value memory unit MME is connected to the switch SW1 and the B contact A of the relay operation signal amplifier AMR1.
The output signal from the input converter 1C1 is input via the MR1b, and the maximum value of the variation ΔI due to the load variation of the feeder wire K up to the present time is always stored.

On the other hand, the calculator CAL calculates and outputs a sensitivity setting value in consideration of a margin to the maximum value of the change amount ΔI from the maximum value memory unit MME. The setting value manual setting device SSET is ΔI
This is for manually setting the set value at the initial operation of the relay body DYR3. The selection switch COS switches between the sensitivity setting value (automatic setting value) from the calculator CAL and the setting value (manual setting value) from the setting value manual setting device SSET depending on whether the setting is automatic or manual. Output. The set value memory unit NSET stores a set value switched and output from the selection switch COS. The comparator OP1 includes a change amount ΔI that is an output signal from the input converter IC1 and a set value memory unit NSET.
And operates when the change amount ΔI is larger than the set value, and outputs an operation signal. The amplifier AMR1 for the relay operation signal is connected to the comparator OP1.
The a-contact AMR1a is turned on to output a trip command for the high-speed circuit breaker HSCB1. The set value display DS receives the output signal from the set value memory unit NSET and displays the current set value.

On the other hand, the maximum value memory unit MME is a memory ME1 that constantly updates and stores the current change amount ΔI in the load current.
And a comparator OP2 that compares the change amount ΔI of the memory ME1 with the change amount ΔI of the memory ME3 and outputs the larger change amount ΔI.
And a memory ME2 for storing an output signal from the comparator OP2,
It comprises a delay circuit T1 that outputs an output signal from the memory M2 with a delay of the time T1, and a memory ME3 that stores output signals from the delay circuit T1. That is, the comparator OP2 compares the current amount of the change amount ΔI input to the memory ME1 with the ΔI amount stored in the memory ME3, and the comparator OP2 gives the larger change amount ΔI to the memory ME2, By delaying the memory content of the accident and giving it to the memory ME3, the memory ME3 stores the maximum value of the variation ΔI due to the load variation of the feeder wire K up to the present time.

Next, the operation of the ΔI relay having such a configuration will be described.

In FIG. 1, in a ΔI current transformer DCT1, a variation ΔI is generated on the CT secondary side in accordance with a variation per hour of a DC current in a DC power circuit (main circuit), and the variation ΔI is Δ
Input to I relay main body DYR3. On the other hand, ΔI relay body
In DYR3, the change amount ΔI from the ΔI current transformer DCT1 is converted into a logic level signal by the input converter IC1. And
One of the converted amounts of change ΔI is input to the comparator OP1 as its comparison element, and the other is input to the switch SW1. The switch SW1 is connected to the ΔI relay body DYR3
This switch is turned on when it is desired to store the maximum change amount ΔI at the time of load. When this switch SW1 is ON and the ΔI
When YR3 is not operating, the variation ΔI, which is an output signal from the input converter IC1, is transferred to the memory ME3 in the maximum value memory unit MME via the switch SW1 and the a contact AMR1a of the relay operation signal amplifier AMR1. It is memorized. In this case, the change amount ΔI from the input converter IC1 is the switch SW1, the contact AMR1a
Is always input to the maximum value memory unit MME when the circuit is formed, but the comparator OP2 outputs the larger change amount ΔI to the memory ME2, so that the memory ME3 of the maximum value memory unit MME has , The maximum value of the change amount ΔI up to the present is stored.

On the other hand, in the arithmetic unit CAL, a sensitivity setting value is calculated based on the maximum value of the variation ΔI from the maximum value memory unit MME, taking into account a margin region for preventing malfunction of the relay as shown in FIG. Then, when the selection switch COS is set to the automatic setting use side, the sensitivity set value from the calculator CAL is stored in the set value memory unit NSET as a set value, and this set value is displayed on the set value display DS. At the same time, it is input to the comparator OP1 as the comparison element. In the comparator OP1, the current variation ΔI from the input converter IC1 is compared with the set value from the set value memory unit NSET. As a result, the comparator OP1 is used only when the current variation ΔI is larger than the set value. OP1 operates to output an operation signal. Then, the relay operation signal amplifier AMR1 is driven by the operation signal from the comparator OP1, and the a contact A
When MR1a is turned ON, a trip command is given to the high-speed circuit breaker HSCB1, and the faulty electric wire K is disconnected from the system.

In FIG. 1, the switch SW1 and the contact AMR1a are provided between the input converter IC1 and the maximum value memory unit MME because the change amount at the time of accident ΔI is not stored in the maximum value memory unit MME. This is for storing only the change amount ΔI at the time of load. That is, the change amount Δ output from the ΔI current transformer DCT1
When I is larger than the sensitivity set value output from the set value memory unit NSET in the comparator OP1, the a contact AMR1a is turned ON.
Then, a trip command is sent to the high speed circuit breaker HSCB1. Here, when the a-contact AMR1a is turned on, this a-contact AMR
The b contact AMR1b linked to 1a is opened. Since the comparator OP1 operates at a high speed, if the comparator OP1 determines that the change amount ΔI output from the ΔI current transformer DCT1 is the change amount at the time of accident ΔI, the change amount at the time of the accident ΔI is, for example, switch
Even if SW1 is closed, it is not input to the maximum value memory unit MME.

Therefore, the a-contact AMR1a and the b-contact AMR1b have the maximum change amount ΔI at the time of an accident exceeding the sensitivity setting value in the maximum value memory unit MME.
An input prohibiting means for prohibiting input to the device is constituted.
Also, the selection switch COS is provided because during the initial operation of the relay, since the maximum change amount ΔI at the time of load is not stored in the relay main body DYR3, a manual settling operation is performed during that time, and the relay main body DYR3 has the maximum change amount. This is to allow time for storing the change amount ΔI.

FIG. 2 is a diagram showing an example of a protection coordination curve when a ΔI relay is used in the present embodiment. That is, since the manual setting value becomes large in the setting of the setting value setter SET1 in FIG. 5 in the conventional method, only the fault current A in the manual setting value range can be detected. Value memory NS
Automatic setting by ET is performed, and this automatic setting value is calculated as the sensitivity setting value considering the margin area from the maximum change amount ΔI at the time of load change stored up to now, so that the optimum setting value suitable for actual operation can be obtained. Become. Then, by using this automatic set value, the change amount ΔI of the fault current B due to the small-scale arc in the sensitivity increase region can be detected. In addition, since the automatic set value has a margin added to the maximum change amount ΔI generated in the actual system, there is no possibility of malfunction due to a load change of the feeder wire K.

As described above, in the ΔI relay of the present embodiment, the maximum value of the change ΔI due to the actual load fluctuation of the feeder wire K up to the present time is stored, and the value obtained by adding the margin area to the maximum value is used for the relay. Since the sensitivity is automatically set as the sensitivity set value, the sensitivity set value can be increased to the maximum and a small-scale arc accident of the wire K can be reliably detected and the wire K can be protected. That is, since the setting value of the relay was set by a human in the past, whether the setting was really in the state of the electric power of the real system was performed, or the setting change amount ΔI was slightly feared due to fear of malfunction of the relay. The setting had to be too large and the sensitivity unnecessarily lowered. However, considering the actual load fluctuations caused by the electric power, on a moment-by-moment basis, the electric vehicle fluctuates very severely depending on the performance, driving pattern, number of passing cars, electric car formation, etc., and the amount of change ΔI also fluctuates. However, when viewed on a daily or weekly basis, the train schedule is fixed on a daily or weekly basis, so the maximum change ΔI due to load fluctuation is also considered to fluctuate at a fixed cycle on a daily or weekly basis. Can be Therefore, as in the present embodiment, once the maximum value of the change amount ΔI due to the actual load fluctuation of the wire K is stored once, the automatic setting value of the relay based on the stored maximum change amount ΔI is as follows. In addition, it is possible to set the optimum sensitivity setting value for the actual operation of the feeder wire, thereby reliably protecting the feeder wire K in a small-scale arc accident, which was impossible in the past.

[Effects of the Invention] As described above, according to the present invention, the maximum value of the variation ΔI due to the actual load fluctuation of the feeder cable up to the present time is stored, and a value obtained by adding a margin to this maximum value is the sensitivity. Since the set value is automatically set, an extremely reliable DC power circuit protection device that can raise the sensitivity set value to the maximum and reliably protect the power cable in the event of a small accident. Can be provided. In addition, for example, it is determined whether the detected change amount ΔI is caused by a load change or an accident by using a sensitivity setting value set in advance by the operator. Therefore, it is possible to determine the change amount ΔI with an abnormally low sensitivity set value at the beginning of operation of the apparatus.

Therefore, for example, even during the calculation period (learning period) of the sensitivity set value based on the variation ΔI caused by the load change, the DC power supply circuit can be properly protected, and the reliability of the device can be improved.

In addition, since the change amount ΔI caused by the load change is prohibited from being used in the calculation as the sensitivity setting value, the reliability of the sensitivity setting value automatically calculated is improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a ΔI relay which is a protection device for a DC power supply circuit according to the present invention, FIG. 2 is a diagram showing a relay coordination curve in the embodiment, and FIG. FIG. 4 is a diagram showing an example of a general system configuration when a ΔI relay system is applied to an electric circuit, FIG. 4 is a diagram for explaining a ΔI amount, and FIG. 5 is a diagram showing a specific example of a ΔI relay conventionally used. Is a block diagram showing a typical configuration example. DCT1 ... ΔI current transformer, DYR3 …… ΔI relay body, IC1…
... Input converter, SW1 ... Switch, MME ... Maximum value memory, CAL ... Calculator, SSET ... Set value manual setting unit, COS ...
... Selection switch, NSET ... Set value memory unit, OP1 ... Comparator, AMR1 ... Relay operation signal amplifier, DS ... Set value display, ME1 ... Memory, OP2 ... Comparator, ME2 ... Memory , T1 ... delay circuit, ME3 ... memory.

Claims (1)

(57) [Claims] 1. A DC power circuit protection device for protecting a DC power circuit connected to a DC bus via a circuit breaker, wherein a change ΔI per hour of a DC current flowing through the DC power circuit is detected. And a change amount ΔI detected by the current change amount detection means, and a change amount ΔI due to a load change of the DC power supply circuit.
A maximum value storage means for storing a maximum value up to the present time; a setting value calculation means for calculating and outputting a sensitivity setting value in consideration of a predetermined margin to the maximum value detected by the maximum value storage means; Setting value setting means for outputting the set sensitivity setting value; and selecting one of the sensitivity setting value output from the setting value calculating means and the sensitivity setting value output from the setting value setting means. Setting value selecting means for outputting, and comparing the change amount ΔI from the current change amount detecting means with the sensitivity setting value from the setting value selecting means, and when it is determined that the change amount ΔI is larger than the sensitivity setting value, the interruption is performed. A comparison means for outputting a trip command to the detector, and a change amount ΔI from the current change amount detection means determined to be larger than the sensitivity set value by the comparison means is prohibited from being input to the maximum value storage means. DC feeding circuit circuit protection device comprising an input prohibition means for.