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In order to determine the rated current for the fuse type required, diagrams are supplied by which the rated current can be deduced from the motor startup current, startup time and startup frequency, thus being able to determine the correct fuse.
HV Fuses for potential transformer protection
Although HV fuses are not able to protect potential transformers efficiently in the case of an internal fault, fuses should be installed as according to the requirements of VDE 0101. In the case of a fault the voltage transformer shall be disconnected from the supply fast as possible in order to limit the fault effects. This is why HV fuses of lowest rated currents are recommended.
HV Fuses for capacitor protection
Whenever capacitors are connected to a network or to a capacitor bank, high inrush peak currents, the peak, the size and duration depend on;
Capacitor size Frequency and inductance of network The closing angle of operation.
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In order to withstand the higher harmonics and to reduce temperature rise, the rated current of the fuses should be at least 2 times the capacitor bank rated current. Increased transient voltages during switching can never be excluded. HV fuses of the next highest voltage range must be used for safety reasons. A selection table classifying HV fuses with the corresponding voltage capacitors is included in the technical annex.
6 Discrimination requirements
Discrimination between HV Fuses
Discrimination problems may occur when distant branch stations in the supply nets are protected by HV fuses in line. In this case the rated current of the upstream fuse should be increased by a factor of 2.
Discrimination between HV and LV Fuses
To prevent the possibility of HV fuse interruption due to a low voltage side fault, a sufficient discrimination must be secured. For comparison, the time-current curves of both fuses have to be converted either to the low voltage or the high voltage level. This is especially important if several LV fuses in parallel are operated in the low voltage output. The fuse with the highest rated current is decisive for discrimination. This operating mode requires comparison of time/current characteristics of the HV fuses with the interrupting to the low voltage characteristics of the designated circuit breaker. For this purpose the time-current characteristics of the HV fuses are level and then compared with the breaker relay characteristics. Sufficient discrimination is given for this operation mode converted when the fuses clear the fault before the circuit breaking capacity is reached. Discrimination between HV Fuses and LV circuit breaker
7 Striker Pin SIBA HV fuses are available with striker pins of force:
50 N (Part No. 30 … y6) variant-type, motor and capacitor fuses. 80 N (Part No. 30 … 13) basic-type, general and DIN style motor fuses. 120 N (Part No. 30 … 14) variant-type, general and DIN style motor fuses.
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The characteristics of both striker pins correspond to IEC 60282-1, VDE 0670 Part 4, and are of the category “medium”. The striker pin system is connected by means of a high resistance parallel conductor. After melting the main fuse elements, the striker pin indicates the operating status of the fuse and can actuate a microswitch for remote indication and/or can trigger a loadbreak switch or a circuit breaker to open. SIBA HV fuses have four basic configurations concerning "Striker" utilization, none , i.e. no striker is incorporated in the fuse and will have a 1 suffix before the .(Amp) rating and is indicated in the fuse article number as 30xxxy1.(Amp). The 80N(Newton's of force) can be incorporated in DIN style fuses with current ratings ranging from 2A to160A and will have a 3 suffix before the .(Amp) rating and is indicated in the article number as 30xxxy 3 .(Amp). The 120N striker is available on DIN style fuses rated 200A and greater will have a 4 suffix before the .(Amp) and is indicated in the fuse article number as 30xxxy4.(Amp). Exceptions to this are the motor R-rated fuses with an R suffix at the end of the article number designation and has the article designation 30xxxy5.zz R . For ratings 6R the striker withstand force is 80N and for ratings 9R the striker
portal: www.siballc.net e-mail: info@sibafuse.com
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