JP2950842B2 - Cable monitoring device and monitoring device scanner - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cable monitoring device using a tan δ measuring device, and more particularly to a monitoring device capable of simultaneously monitoring a plurality of cables and a monitoring device of this type. The present invention relates to a scanner for a cable monitoring device to be applied.

[Prior Art] Insulation measurement is performed in order to prevent an electrical breakdown accident of a power cable. As a method of performing the insulation measurement in a hot-line state without a power failure, a hot-line measurement method has been developed.

As such a live line measuring device, there is a live line tan δ measuring device as shown in FIG. In the hot-line tan δ measuring device shown in the figure, first, a current transformer CT is attached to the ground line 2 of the cable under test 1 to detect a charging current, and from a far end of the cable under test 1 via a rod-shaped voltage divider R. A current in phase with the voltage applied to the cable under test is detected. These detection currents are respectively converted into voltages es and ex by a current / voltage conversion circuit. The phase of the voltage es is set to 90% because the part of the charging current whose phase completely advances 90 ° from the applied voltage is proportional to the capacitance.
The capacitance is measured by advancing by 90 ° by the {phase shift circuit} and balancing the capacitance component of the voltage ex with the reference voltage. Also, tan δ is measured from the ratio of the applied voltage and the in-phase component of the charging current to the capacitance component.

Such a hot-line tan δ measuring device can measure the insulation of a power cable in a hot-line state, and can increase the measurement accuracy by using a two-stage CT as a current transformer CT. When used together, reliable deterioration diagnosis can be performed as a comprehensive insulation monitoring system.

[Problems to be Solved by the Invention] However, the conventional hot-line tan δ measuring device described above can measure only one cable with one device. Therefore, in order to measure a plurality of cables, it is necessary to use a corresponding device. It must be prepared or replaced by the measuring terminals, ie, the voltage divider and the current transformer. However, all of these methods have problems in terms of cost and safety, and switching means such as a manual switch cannot be adopted from a safety point of view, and when a live-line tanδ measuring device is incorporated into a comprehensive insulation monitoring system. Was hindered.

[Object of the Invention] The present invention solves such a conventional problem, and
It is an object to provide a monitoring device for a plurality of cables using an nδ measuring device and a scanner for such a monitoring device.

[Means for Solving the Problems] A cable monitoring device of the present invention that achieves the above object includes a voltage detection unit attached to each cable to be measured,
A current detection unit attached to each ground line of each cable to be measured, a voltage signal from each of the voltage detection units and a current signal from each of the current detection units, and a voltage signal corresponding to one cable to be measured And a scanner for selectively outputting a current signal and a voltage signal and a current signal from the scanner.
A tan δ measuring unit for measuring nδ, and a relay control unit for controlling a switching operation of a voltage signal and a current signal in the scanner, wherein the scanner switches and connects a ground line and a tan δ measuring unit to each current detecting unit. And a current switching unit having a relay composed of:

The scanner for a monitoring device according to the present invention further includes a tan δ measuring unit of the cable monitoring device that measures tan δ based on a current signal from each ground line of each cable to be measured and a voltage signal from each cable to be measured. A scanner for selectively outputting a voltage signal and a current signal corresponding to a cable, wherein the scanner inputs a current signal from each ground wire of each cable to be measured and outputs one of the current signals to a tanδ measuring unit. Current switching section, a voltage switching section for inputting a voltage signal from each cable to be measured and outputting one of the voltage signals to the tanδ measuring section, and a relay control for controlling each switching operation of the current switching section and the voltage switching section. The relay control section is composed of a solid state relay connected to the microcomputer, and the current switching section is configured in two stages of switching and connecting the ground line and the tanδ measuring section to each current detecting section. It has a relay to be performed.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing an overview of a power cable monitoring device to which the present invention is applied. A current transformer is used as a current detection unit attached to each of the ground wires 11a, 12a, and 13a of the cables under test 11, 12, and 13. (Hereinafter referred to as CT) 21, 22, 23, cable under test 1
Voltage divider 3 as voltage detector attached to 1, 12, 13
1, 32, 33 and a transformer for grounding (hereinafter referred to as GPT) 40,
A scanner 50 that switches a current signal from a CT and a voltage signal from a voltage divider or a GPT and outputs one current signal and one voltage signal, and a tan δ measuring unit that measures tan δ based on the voltage signal and the current signal output from the scanner 50 The microcomputer 70 includes a microcomputer 70 (hereinafter, referred to as a microcomputer) for controlling the scanner 50 and storing and processing data of the tan δ measuring unit 60, and an alarm generation circuit 80 for generating an alarm based on a signal from the microcomputer 70. You.

Although the figure shows only three cables 11, 12, and 13 to be measured, more than three cables may be used.

CT21, 22, 23 is preferably a two-stage CT and the cable to be measured 1
Detect charging currents of 1, 12, and 13. Voltage detector is voltage divider 3
Although GPT40 is used in combination with 1, 32, and 33, only one of them may be used. For example, in the case of a 6.6 kVCV cable, the voltage dividers 31, 32, and 33 have a resistance of about 3 MΩ, so that a current of about 1.3 mA can be extracted as a voltage signal.

As shown in FIG. 2, the scanner 50 includes a current switching unit 51, a voltage switching unit 52, and a relay control unit 53. The current switching unit 51 switches the current signal from each cable to be measured,
The voltage switching unit 52 selects and outputs a current signal of the cable under test, and includes a plurality of sets of relays corresponding to the current signal. The voltage switching unit 52 switches between a voltage divider and GPT and a voltage from the voltage divider or GPT. It comprises a plurality of relays for switching signals and selecting and outputting a voltage signal of one cable under test. The relay control unit 53 includes a current switching unit 51 and a voltage switching unit 52.
And an interface between each of the relays and the microcomputer 70, and comprises a photocoupler-insulated solid state relay (hereinafter, referred to as SSR).

The tan δ measurement unit 60 includes a current / current conversion circuit 61 for a current signal, a current / voltage conversion circuit 62 for a voltage signal, and a 90 ° phase shift circuit for changing the phase of the voltage signal, as shown in FIG. 63, an auto-balancing circuit 64 for measuring the capacitance (C) and tan δ by balancing the in-phase component of the applied voltage or 90 ° ahead of the applied voltage in the voltage signal and the current signal, and And a display section (not shown) for displaying tanδ.

In the tan δ measurement unit 60, the current signal and the voltage signal are converted into voltages e and es by current / voltage conversion circuits 61 and 62, respectively. Since the phase of the current signal whose phase is completely 90 ° ahead of the applied voltage is proportional to the capacitance, the phase of the voltage es is advanced by 90 ° by the 90 ° phase shift circuit, and the static of the voltage ex is set based on this. The capacitance is measured by balancing the capacitance component. In addition, tan δ is measured from the ratio of the in-phase component to the applied voltage and the capacitance component of the current signal.

The microcomputer 70 controls the relays of the current switching unit 51 and the voltage switching unit 52 by transmitting and receiving signals to and from the relay control unit 53 of the scanner 50, confirms the open / closed state of the relay, and measures tan δ. The data measured by the unit 60 is stored. That is, the tan δ value is compared and determined with preset data, and a signal is sent to the alarm generation circuit 80 based on the result. The microcomputer 70 is also configured to input measurement data such as voltage and current applied to each cable to be measured.

The alarm generating circuit 80 includes an alarm unit such as a lamp and an alarm sound and an alarm unit driving circuit, and generates an alarm indicating that there is an abnormality in the cable to be measured by a signal from the microcomputer 70.

Next, a more detailed configuration of the scanner 50 will be described. The current switching section 51 of the scanner 50 is provided as shown in FIG.
A set of relays [ry1, ry2], [ry3, ry4] and [ry5, r] for inputting a current signal from the CT and selecting one current signal
y6]. In this embodiment, the CT has three terminals for extracting a current signal of one cable to be measured. The tan δ measuring unit 60 also has three input terminals for inputting a current signal.

The set of relays prevents generation of surge voltage due to CT by switching each current signal in two stages. Also, each set of relays is connected to the microcomputer 70 via the SSR of the relay control unit 53 described later, and the microcomputer 70
Is driven and controlled. In addition, each relay set is linked to each relay set, and a contact [Ry
1, Ry2], [Ry3, Ry4] and [Ry5, Ry6]. These contacts are connected to the microcomputer 70 via another SSR, whereby a signal indicating the open / close state of each set of relays is sent to the microcomputer 70.

As shown in FIG. 5, the voltage switching unit 52 includes voltage dividers 31, 31,
A relay ry7 for switching to either 33 or GPT40 and relays ry8, ry9, for inputting the voltage signal from each voltage divider and the voltage signal from GPT40 and selecting one voltage signal.
It consists of ry10, ry11, ry12, and ry13.
A voltage / current conversion resistor 35 is provided between the GPT 40 and the relay. These relays ry7 to ry13 are connected to the microcomputer 70 via the SSR of the relay control unit 53 in the same manner as the relay of the current switching unit 51, and are driven and controlled by the microcomputer 70. Also, each relay ry7 ~ ry13
Has a contact Ry7 that works with it and checks its status.
To Ry13 are provided. These contacts Ry7 to Ry13 are also connected to the microcomputer 70 via another SSR similarly to the contacts Ry1 to Ry6 of the current switching unit 51, whereby a signal notifying the open / close state of each relay is sent to the microcomputer 70. Can be

FIG. 6 shows the configuration of the relay control unit 53. Relay control section
Reference numeral 53 denotes a group of SSRs (SSR1 to SSR13) connected to the microcomputer 70 for driving and controlling the relays ry1 to ry13 of the current switching unit 51 and the voltage switching unit 52, and opening and closing of the contacts Ry1 to Ry13. A group of SSRs (SSR14 to SSR2) connected to the microcomputer 70 to check the status
6).

The SSRs of both groups have the opposite input and output, and both consist of photocoupler-isolated solid-state relays.
A microcomputer connected to the isolated parallel output (or input) module of the microcomputer 70
Provides a secure interface with the 70. In the group (SSR1 to SSR13), for example, when a signal is sent from the microcomputer 70 to SSR1, ry1 turns ON. Also, in the group (SSR14 to SSR26), when ry1 turns ON, R
When Y1 is turned ON, a signal is sent to the microcomputer 70 via the SSR 14, and the fact is confirmed.

 The operation in the above configuration will be described.

On the input side of the current switching unit 51 and the voltage switching unit 52 of the scanner 50, the CT2 attached to each of the cables under test 11, 12, 13 is connected.
Current and voltage signals from 1, 22, 23, voltage dividers 31, 32, 33 and CRT 40 are sent. In the initial state of the scanner 50, all the relays ry1 to ry13 are on the ground side, that is, in the OFF state. Here, in order to select the cable under test 11, ry2 is turned on first, and then ry1 is turned on. By switching in two stages in this way, there is no surge voltage generated by the CT and switching can be performed safely. Similarly, turn on relay ry7
After switching to the voltage divider side, turn on relay ry8.
Control of these relays ry1, ry2, ry7 and ry8 is performed by controlling signals from the microcomputer 70 by using the SSR1 of the relay control unit 53,
This is done by activating SSR2, SSR7 and SSR8. Also, when ry1, ry2, ry7 and ry8 are turned on and RY1, RY2, RY7 and RY8 linked with them are turned on, SS
The microcomputer sends a signal from R14, SSR15, SSR20 and SSR21 to the microcomputer 70 and turns on the microcomputer.
Confirmed by 70.

In this way, switching is performed by combining the SSR and contact relays, so safety can be ensured.In addition, direct switching using only the SSR causes the phase to be out of order due to the reactance of the SSR, making it impossible to measure minute phase differences. On the other hand, highly accurate measurement is possible.

The current signal and the voltage signal of the cable under measurement 11 selected by the scanner 50 are sent to the tan δ measurement unit 60, respectively.

The tan δ measurement unit 60 measures the capacitance by balancing the voltage signal with the component that is 90 ° ahead of the voltage of the current signal as described above, and also measures the capacitance of the current signal in phase with the voltage. The tan δ is measured and displayed from the ratio of the capacitance components, and these data are sent to the microcomputer 70.

The microcomputer 70 compares these data with preset data, and when it is determined that the deterioration has progressed, sends a signal to the alarm generation circuit 80, thereby generating an alarm such as an alarm sound. I do.

If it is determined that the cable is sound, the cable is switched to the next cable to be measured, and similar measurement and determination are sequentially performed.

In the above-described embodiment, the configuration in which the relay control unit 53 and the microcomputer 70 are insulated by the photocoupler has been described. However, optical transmission may be used for the interface between the relay control unit 53 and the microcomputer 70. It is possible.

[Effects of the Invention] As is clear from the above embodiments, according to the present invention,
Adopting a scan that combines a contact relay and SSR,
As a result, current signals and voltage signals from a plurality of cables to be measured are switched, so that a plurality of power cables tanδ can be measured extremely safely and accurately.

In addition, according to the scanner of the present invention, the switching of the relay can be controlled by the microcomputer.
It is possible to incorporate δ measurements into a comprehensive power cable insulation monitoring system.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a cable monitoring device according to the present invention, FIG. 2 is a diagram showing an embodiment of a scanner, FIG. 3 is a block diagram showing a tan δ measuring section, FIGS. FIG. 6 is a diagram showing a part of the circuit of the scanner, and FIG. 7 is a diagram showing a conventional hot-line tan δ measuring device. 11, 12, 13… Cable to be measured 11a, 12a, 13a… Ground wire 21, 22, 23… CT (current detector) 31, 32, 33… Voltage divider (voltage detector) 40… GPT (Voltage detection unit) 50 Scanner 51 Current switching unit 52 Voltage switching unit 53 Relay control unit 60 tanδ measuring unit 70 Microcomputer ry1 to ry13 Relays SSR1 to SSR26 Solid State relay

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-254078 (JP, A) JP-A-48-83712 (JP, A) JP-A-58-90826 (JP, A) 169574 (JP, A) JP-A-61-41974 (JP, A) JP-A-62-242869 (JP, A) JP-A-2-21278 (JP, A) JP-A-64-59086 (JP, A) JP-A-62-39777 (JP, A) JP-A-59-211867 (JP, A) JP-A-60-25976 (JP, U) JP-A-1-118376 (JP, U) (58) Fields investigated (Int.Cl. ⁶ , DB name) G01R 31/08-31/20

Claims (2)

(57) [Claims] 1. A voltage detector attached to each cable under test, a current detector attached to each ground line of each cable under test, voltage signals from each of the voltage detectors and the current detection A scanner for inputting current signals from each of the sections and selectively outputting a voltage signal and a current signal corresponding to one cable to be measured, and a tanδ measurement for measuring tanδ based on the voltage and current signals from the scanner And a relay control unit that controls a switching operation of a voltage signal and a current signal in the scanner. The scanner includes a ground line and the tanδ in each of the current detection units.
A cable monitoring device comprising a current switching unit having a relay configured in two stages for switching and connecting to a measuring unit. 2. The method according to claim 1, wherein a current signal from each ground line of each cable to be measured and a voltage signal from each cable to be measured are used as a signal.
A scanner that selectively outputs a voltage signal and a current signal corresponding to one cable to be measured to a tan δ measuring unit of a cable monitoring device that measures nδ, wherein the scanner is configured to output each of the cables to be measured. A current signal from a ground line is input, and one of the current signals is
a current switching unit for outputting to the δ measuring unit, and a voltage signal from each of the cables to be measured, and one of the voltage signals
a voltage switching unit that outputs to the nδ measurement unit; and a relay control unit that controls each switching operation of the current switching unit and the voltage switching unit.The relay control unit includes a solid-state relay connected to a microcomputer. The current switching unit includes a ground line and the tan
A scanner for a cable monitoring device, comprising a relay configured in two stages for switching and connecting to a δ measurement unit.