Technical Journal - November 2013 Current limiting feature in ......Technical Journal - November...
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With increase in overall size of distribution transformer ratings in industry to support power demand required has led to increase network fault current. This leading to selection of various switching and protection components of motors to be sized for rated fault current. The implications are very high in terms of space requirement and overall project cost whether the requirement is for power distribution panels or motor control panels. With right engineering and selection of components one can establish a very compact and economical solution without compromising reliability and safety. In this document we will analyze and see how we can implement optimized solution for network which is fault level up to 100kA in 440volts network and 50kA at 690volts. Today there are current limiting devices which are available which can be used to increase the short breaking capacity of downstream circuit breakers or manual motor starters. These current limiting devices provide increased area of application for protecting devices which are lower breaking capacity. The short-circuit limiting device to be selected such that it provides full selectivity for any downstream Motor protection combination (multiple feeders). In case of a short- circuit in one of the circuits, the limiter is required ensure that the manual motor Starters to break the faulty circuit without forcing the upstream protection device to trip. All other motor starters in the group remain functional. Current limiting feature in low voltage networks Technical Journal - November 2013 These current limiting devices provide extensive benefits Maximum system availability – Back-up up to highest short-circuit currents – Full selectivity for any downstream motor or line protection combination Compact design – Over all cabinet sizes reduces substantially Cost saving solution – Selection of devices made very simple – Reduced cabinet size provides cost benefit with lesser material cost. – One current limiter for multiple downstream devices either manual motor starters or miniature circuit breaker Reliability – The product is fully tested for its performance Safety – Low let through energy values – Prospective peak current is limited The following scheme provides insight into the way network is connected.
Transcript of Technical Journal - November 2013 Current limiting feature in ......Technical Journal - November...
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With increase in overall size of distribution transformer ratings in industry to support power demand required has led to increase network fault current. This leading to selection of various switching and protection components of motors to be sized for rated fault current.
The implications are very high in terms of space requirement and overall project cost whether the requirement is for power distribution panels or motor control panels. With right engineering and selection of components one can establish a very compact and economical solution without compromising reliability and safety.
In this document we will analyze and see how we can implement optimized solution for network which is fault level up to 100kA in 440volts network and 50kA at 690volts.
Today there are current limiting devices which are available which can be used to increase the short breaking capacity of downstream circuit breakers or manual motor starters. These current limiting devices provide increased area of application for protecting devices which are lower breaking capacity.
The short-circuit limiting device to be selected such that it provides full selectivity for any downstream Motor protection combination (multiple feeders). In case of a short- circuit in one of the circuits, the limiter is required ensure that the manual motor Starters to break the faulty circuit without forcing the upstream protection device to trip. All other motor starters in the group remain functional.
Current limiting feature in low voltage networksTechnical Journal - November 2013
These current limiting devices provide extensive benefits
Maximum system availability – Back-up up to highest short-circuit currents– Full selectivity for any downstream motor or line protection
combination
Compact design– Over all cabinet sizes reduces substantially
Cost saving solution– Selection of devices made very simple – Reduced cabinet size provides cost benefit with lesser
material cost.– One current limiter for multiple downstream devices either
manual motor starters or miniature circuit breaker
Reliability– The product is fully tested for its performance
Safety– Low let through energy values– Prospective peak current is limited
The following scheme provides insight into the way network is connected.
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As a user the important aspect which is to be taken into consideration is that the current limiting devices is third party tested and manufacturer provides typical combination in form of table for right selection.
These current limiting devices have wide area of applications like…– Ship industry where space is a constraint– Mining application where compact panels provides great
advantage.– Oil and Gas where reliability and safety is of prime
importance.– Wind mill generator where compact design is very
important.– Process industries like Cement, Paper, Pharma and Sugar.
ABB provides excellent solution on current limiting devices. The solution complies with both European (IEC – available in multiple poles) and American regulation. Typical configuration is as shown below. The solution offer 2 different types
– Solution with Auto reset (Up to 100A)– Solution with Manual resent (Up to 63A)
The chart below provides coordination between upstream and downstream devices.
The chart complies with fault level and voltage indicated in the below tabular column.
Down Stream devices (MS/MO 132)
Self reset type limiter Manual type limiter
Rated current 32 63 100 32 63
0.1 – 2.5A
4
6.3
10
16
20
25
32
Icu=Ics (IEC 947-2) Rating (kA)
240/415V, 50/60Hz 100
254/440V, 50/60Hz 100
277/480V, 50/60Hz 65
289/500V, 50/60Hz 65
346/600V, 50/60Hz 65
400/690V, 50/60Hz 50
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