MITSUBISHI ELECTRIC Low-voltage Products
Continuously Monitoring of Insulation by PLC
– Production Equipment Preventive Maintenance Support –
Early Detection of Insulation Deterioration in Production Equipment
- Since this module is connected directly to the PLC in the control panel, leakage current from points close to loads can be measured easily without the need for additional installation space.
- The module can detect troubles caused by earth leakage (ground fault) and monitor the insulation of motor loads in the production equipment. It does not overlook ongoing insulation deterioration.
- Upper-limit monitoring values for alarms can be set in two stages. Insulation deterioration/condition is detected at each stage, enabling countermeasures before equipment stoppage/malfunction.
Constant Monitoring for Insulation Deterioration of Equipment Using I0r Method
- The module can measure resistive-component leakage current (I0r). Even on circuits which cannot be monitored for insulation using the conventional I0 method, such as inverter circuits on which capacitor component leakage current (I0c) is large, the module removes the I0c component and can correctly monitor the leakage current caused by insulation deterioration.
- The module constantly measures the resistive-component leakage current (I0r) even while equipment is running. It detects any sign of insulation deterioration without power interruption.
Since leakage current (I0) is affected by the I0c of the whole equipment, the I0r measurement is effective for insulation deterioration diagnosis
Method of leakage current measurement (I0 and I0r measurements)
- I0r :
- Leakage current caused by insulation deterioration (leakage current from resistive component)
- I0c :
- Leakage current flowing even in good insulation condition (leakage current from electrostatic capacity)
- I0 :
- Leakage current obtained by synthesizing I0r and I0c (vector synthesis)
The I0c fluctuates on equipment with long wiring distance or inverter devices and filters.
(1) General specifications
| Item | Specification | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Phase wire system | Single-phase 2-wire, single-phase 3-wire and 3-phase 3-wire systems common use | |||||||||
| Instrument rating | Voltage circuit*1*2 | Single-phase 2-wire | 110VAC and 220VAC common use | |||||||
| 3-phase 3-wire | ||||||||||
| Single-phase 3-wire | 110VAC (between wires 1-2, between wires 2-3), 220VAC (between wires 1-3) |
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| Leakage current circuit | AC1A (ZCT is used. The current is the primary current of ZCT.) | |||||||||
| Frequency | 50-60Hz (automatic frequency selection) | |||||||||
| Main unit tolerances (excluding ZCT) |
Leakage current |
±2.5% (10% to 100% of rating) ±2.5mA (  10% of rating)
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| Resistive-component leakage current | ||||||||||
| (The resistive-component leakage current does not include electrostatic capacity.) | ||||||||||
| Number of measurement circuits | 2 circuits*3 | |||||||||
| Data refresh period |
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| Response time |
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| Power outage compensation | Backup to nonvolatile memory (Saved items: Setting values, max. value and its occurrence date/time, alarm occurrence times) |
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| Number of occupied I/O points | 16 points (I/O assignment: intelligent 16 points) | |||||||||
- *1 :
- The module can be connected directly to 110V and 220V. To connect to 440V, an external voltage transformer (VT) is necessary. Leakage current (I0, I0r) cannot be measured without voltage input.
- *2 :
- I0r can be measured on a single-phase 3-wire or 3-phase 3-wire delta circuit. On special grounded circuits, such as 3-phase 3-wire star circuits, high-resistance grounded circuits and capacitor grounded circuits, only I0 can be measured.
- *3 :
- Leakage current (I0 and I0r) of CH1 and CH2 can be measured only on circuits when the voltage input was on the same system.
(2) Measuring items
| Measurement items | |||
|---|---|---|---|
| Details | |||
| Leakage current (I0) | Current value | ||
| Max. value | |||
| Occurrence date/time of max. value | |||
| Number of first stage alarm occurrences | |||
| Number of second stage alarm occurrences | |||
| Resistive-component leakage current (I0r) | Current value | ||
| Max. value | |||
| Occurrence date/time of max. value | |||
| Number of first stage alarm occurrences | |||
| Number of second stage alarm occurrences | |||
(3) Specifications for Zero-phase Current Transformer (ZCT)
Split-type Zero-phase Current Transformer
| Item | Specification | ||||
|---|---|---|---|---|---|
| Model name | CZ-22S | CZ-30S | CZ-55S | CZ-77S | CZ-112S |
| Hole diameter [mm] | 22 | 30 | 55 | 77 | 112 |
| Allowable current | See the following table "Penetrable max. wire size and allowable current of ZCT" | ||||
| Mass [kg] | 0.5 | 0.6 | 1.8 | 2.8 | 6.0 |
| Rated short-time current | 50kA (peak value is 100kA) | ||||
Through-type Zero-phase Current Transformer
| Item | Specification | |||||
|---|---|---|---|---|---|---|
| Model name | ZT15B | ZT30B | ZT40B | ZT60B | ZT80B | ZT100B |
| Hole diameter [mm] | 15 | 30 | 40 | 60 | 80 | 100 |
| Allowable current | See the following table “Penetrable max. wire size and allowable current of ZCT” | |||||
| Mass [kg] | 0.2 | 0.4 | 0.6 | 2.0 | 2.6 | 3.3 |
| Rated short-time current | 50kA (peak value is 100kA) | |||||
Zero-phase Current Transformer with primary conductor
| Item | Specification | ||
|---|---|---|---|
| Model name | ZTA600A | ZTA1200A | ZTA2000A |
| Allowable current [A] | 600 | 1200 | 2000 |
| Mass [kg] | 6.5 | 11 | 27 |
| Number of poles | 3 | ||
| Rated voltage | AC600V | ||
| Rated short-time current | 100kA (peak value) | ||
Penetrable max. wire size and allowable current of ZCT
| Wiring method | Penetrable max. wire size (mm2) (allowable current (A)) |
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|---|---|---|---|---|---|---|---|
| Split-type | |||||||
| Phase wire system | No. of wires | Wire type | CZ-22S | CZ-30S | CZ-55S | CZ-77S | CZ-112S |
| Single-phase 2-wire | 2 | 600-V vinyl wire(IV wire) | 22 (115) |
60 (217) |
250 (556) |
500 (842) |
– |
| 600-V cross-linked polyethylene insulated wire with single core (CV wire) |
22 (130) |
38 (190) |
200 (545) |
500 (920) |
1000 (1465) |
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| Single-phase 3-wire 3-phase 3-wire |
3 | 600-V vinyl wire(IV wire) | 22 (115) |
38 (162) |
200 (496) |
500 (842) |
– |
| 600-V cross-linked polyethylene insulated wire with single core (CV wire) |
14 (100) |
22 (135) |
150 (455) |
325 (760) |
800 (1285) |
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| Wiring method | Penetrable max. wire size (mm2) (allowable current (A)) |
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|---|---|---|---|---|---|---|---|---|
| Through-type | ||||||||
| Phase wire system | No. of wires | Wire type | ZT15B | ZT30B | ZT40B | ZT60B | ZT80B | ZT100B |
| Single-phase 2-wire | 2 | 600-V vinyl wire(IV wire) | 14 (88) |
60 (217) |
150 (395) |
325 (650) |
600 (992) |
800 (1185) |
| 600-V cross-linked polyethylene insulated wire with single core (CV wire) |
2 (33) |
38 (190) |
60 (260) |
250 (655) |
400 (870) |
600 (1140) |
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| Single-phase 3-wire 3-phase 3-wire |
3 | 600-V vinyl wire (IV wire) | 8 (61) |
38 (162) |
100 (298) |
250 (556) |
500 (842) |
725 (1095) |
| 600-V cross-linked polyethylene insulated wire with single core (CV wire) |
2 (33) |
22 (135) |
60 (260) |
200 (560) |
325 (760) |
600 (1140) |
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Remarks
- (1) :
- Note that the wire thickness may vary slightly depending on the manufacturer.
- (2) :
- The IV wire applies to cases where insulators are used.
- (3) :
- The CV wire applies to cases of installation in a covered conduit in air. (Cables of 600mm2 or more have various structures. The values are shown for reference.)
