An insulation monitoring device monitors the ungrounded system between an active phase conductor and earth. It is intended to give an alert (light and sound) or disconnect the power supply when the resistance between the two conductors drops below a set value, usually 50 kΩ (sample of IEC standard for medical applications). The main advantage is that the ungrounded or floating system allows a continuous operation of important consumers such as medical, chemical, military, etc.
Some manufacturers of monitors for these systems are capable of handling VFDs (Variable Frequency (Speed) Drives). Most, however are not due to issues with the DC-portions of the VFDs.
Most monitors work by injecting low level DC on the line and detecting. Some manufacturers use a patented AMP-monitoring principle (Adapted Measuring Pulse)[citation needed]
Insulation Monitoring Devices (IMD) according to IEC 61557-8edit
This part of IEC 61557 specifies requirements for insulation monitoring devices (IMD), which permanently monitor the insulation resistance RF to earth of unearthed a.c. IT systems, of a.c. IT systems with galvanically connected d.c. circuits having nominal voltages up to 1 000 V a.c., as well as of unearthed d.c. IT systems with voltages up to 1 500 V d.c. independent from the method of measuring.[1]
According to 61557-8: Insulation monitoring devices must be able to monitor both symmetrical and asymmetrical insulation faults according to their specified measuring principle. A symmetrical fault in insulation occurs when the insulation resistance of all conductors in the network to be monitored is (approximately) evenly reduced. An unsymmetrical fault in insulation occurs when the insulation resistance, e.g. of one conductor is reduced much more than that of the remaining conductor(s). Relays, which use the unbalance voltage (3 voltmeter method), are not insulation monitoring devices according to this standard. Under special network conditions, a combination of several measurement methods may be necessary to fulfill the monitoring task, including an asymmetry monitoring.[2]
Terminologyedit
Terminology differs by region and by market segment.
For the system type different terms are used: "IT system" (lat. Isolation Terra) vs. "floating system" vs. "ungrounded system".[3]
For the monitoring device different terms are used: "Insulation monitoring device" vs. "ground fault relay" vs. "ground fault detector" vs. "LIM" (Line Isolation Monitor)
Standardsedit
IEC 61557-8:2014, "Electrical safety in low voltage distribution systems up to 1 000 V a.c. and 1 500 V d.c. - Equipment for testing, measuring or monitoring of protective measures - Part 8: Insulation monitoring devices for IT systems"
IEC 61557-9:2014, "Electrical safety in low voltage distribution systems up to 1000 V a.c. and 1500 V d.c. - Equipment for testing, measuring or monitoring of protective measures - Part 9: Equipment for insulation fault location in IT systems"
Literatureedit
Wolfgang Hofheinz: Protective Measures with Insulation Monitoring VDE Application of Unearthed IT Power Systems in Industry, Mining, Railways, Marine/ Oil and Electric/Rail Vehicles, ISBN978-3-8007-2958-6, E-Book: ISBN978-3-8007-4106-9
Further readingedit
IEC 61557-8 Electrical safety in low voltage distribution systems up to 1 000 V a.c. and 1 500 V d.c. – Equipment for testing, measuring or monitoring of protective measures – Part 8: Insulation monitoring devices for IT systems
^"Insulation monitoring: The concept". Bender GmbH & Co. KG. 2020-12-20.
^"Application and Operation of Insulation Monitors in Unearthed (floating-IT) Rail Signal Power Systems". IEEE Xplore. Retrieved 2020-12-20.
January 01, 1970
insulation, monitoring, device, insulation, monitoring, device, monitors, ungrounded, system, between, active, phase, conductor, earth, intended, give, alert, light, sound, disconnect, power, supply, when, resistance, between, conductors, drops, below, value, . An insulation monitoring device monitors the ungrounded system between an active phase conductor and earth It is intended to give an alert light and sound or disconnect the power supply when the resistance between the two conductors drops below a set value usually 50 kW sample of IEC standard for medical applications The main advantage is that the ungrounded or floating system allows a continuous operation of important consumers such as medical chemical military etc Some manufacturers of monitors for these systems are capable of handling VFDs Variable Frequency Speed Drives Most however are not due to issues with the DC portions of the VFDs Most monitors work by injecting low level DC on the line and detecting Some manufacturers use a patented AMP monitoring principle Adapted Measuring Pulse citation needed Contents 1 Insulation Monitoring Devices IMD according to IEC 61557 8 2 Terminology 3 Standards 4 Literature 5 Further reading 6 ReferencesInsulation Monitoring Devices IMD according to IEC 61557 8 editThis part of IEC 61557 specifies requirements for insulation monitoring devices IMD which permanently monitor the insulation resistance RF to earth of unearthed a c IT systems of a c IT systems with galvanically connected d c circuits having nominal voltages up to 1 000 V a c as well as of unearthed d c IT systems with voltages up to 1 500 V d c independent from the method of measuring 1 According to 61557 8 Insulation monitoring devices must be able to monitor both symmetrical and asymmetrical insulation faults according to their specified measuring principle A symmetrical fault in insulation occurs when the insulation resistance of all conductors in the network to be monitored is approximately evenly reduced An unsymmetrical fault in insulation occurs when the insulation resistance e g of one conductor is reduced much more than that of the remaining conductor s Relays which use the unbalance voltage 3 voltmeter method are not insulation monitoring devices according to this standard Under special network conditions a combination of several measurement methods may be necessary to fulfill the monitoring task including an asymmetry monitoring 2 Terminology editTerminology differs by region and by market segment For the system type different terms are used IT system lat Isolation Terra vs floating system vs ungrounded system 3 For the monitoring device different terms are used Insulation monitoring device vs ground fault relay vs ground fault detector vs LIM Line Isolation Monitor Standards editIEC 61557 8 2014 Electrical safety in low voltage distribution systems up to 1 000 V a c and 1 500 V d c Equipment for testing measuring or monitoring of protective measures Part 8 Insulation monitoring devices for IT systems IEC 61557 9 2014 Electrical safety in low voltage distribution systems up to 1000 V a c and 1500 V d c Equipment for testing measuring or monitoring of protective measures Part 9 Equipment for insulation fault location in IT systems Literature editWolfgang Hofheinz Protective Measures with Insulation Monitoring VDE Application of Unearthed IT Power Systems in Industry Mining Railways Marine Oil and Electric Rail Vehicles ISBN 978 3 8007 2958 6 E Book ISBN 978 3 8007 4106 9Further reading editIEC 61557 8 Electrical safety in low voltage distribution systems up to 1 000 V a c and 1 500 V d c Equipment for testing measuring or monitoring of protective measures Part 8 Insulation monitoring devices for IT systems The IT earthing system unearthed neutral in LV Ungrounded Power Supply Systems in Medical SitesReferences edit IEC 61557 8 IECEE 2020 12 20 Insulation monitoring The concept Bender GmbH amp Co KG 2020 12 20 Application and Operation of Insulation Monitors in Unearthed floating IT Rail Signal Power Systems IEEE Xplore Retrieved 2020 12 20 Retrieved from https en wikipedia org w index php title Insulation monitoring device amp oldid 1165647682, wikipedia, wiki, book, books, library,
