MITSUBISHI ELECTRIC Low-voltage Products
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Energy Measuring Devices Insulation Monitoring Module Programmable Controllers, MELSEC-Q Series

Continuously Monitoring of Insulation by PLC

– Production Equipment Preventive Maintenance Support –

Features

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.
Conventional insulation monitoring equipment System where leakage occurs can be identified, but itís not possible to detect insulation deterioration in equipment.Insulation Monitoring Unit Insulation monitoring pinpoints the problematic equipment, making it possible to recognize deteriorated insulation location early on!

Constant Monitoring for Insulation Deterioration of Equipment Using I0r Method

The I0r method stated in the "Standard Specifications for PublicWorks Construction (Electric Equipment Work)" edited by the Ministry of Land, Infrastructure, Transport and Tourism is used.
  • 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)

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.

The I0c fluctuates on equipment with long wiring distance or inverter devices and filters.

Advantages of Introducing the Insulation Monitoring Module

Conventional systems

Measurement of insulation resistance with wiring disconnected during inspection / Power must be suspended to set the equipment in the non-voltage state / When leakage current is detected, power supply stops suddenly / Insulation deterioration cannot be detected easily due to the I0c component

Insulation Monitoring Module

Constant monitoring of leakage current during operationReduction of labor for insulation resistance test / No need to suspend power supply to equipment / Early detection of insulation deterioration signs / Improvement of availability and reduction of product loss through measures taken before suddens top

General Specifications & Measured Items

(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)
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)
Resistive-component leakage current
(The resistive-component leakage current does not include electrostatic capacity.)
Number of measurement circuits 2 circuits*3
Data refresh period
Leakage current : 2 sec or less
Resistive-component leakage current : 10 sec or less
Response time
Leakage current : 4 sec or less
Resistive-component leakage current : 30 sec or less
Power outage compensation Backup to nonvolatile memory
(Saved items: Setting values, max. value and its occurrence date/time, alarm occurrence times)
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))
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)
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)
Wiring method Penetrable max. wire size (mm2)
(allowable current (A))
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)
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)

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.)