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sqd-app-guide-2-25c.pdf

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The energy let through by a circuit breaker determines the minimum cable size required downstream. Current limiting breakers let through less energy, so their cable size ratings do not indicate continuous current capacity. Upstream breakers can permit smaller downstream breakers if the upstream breaker limits fault current to a level the downstream breaker can interrupt. Cascading charts list compatible upstream and downstream breaker combinations.

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Sec2 25 Commercial and industrial solutions for 3 phase distribution Energy let through 2 I2 t Energy let through The energy let through by a breaker determines the minimum size of the downstream cable. Minimum cable size required based on I2 t let through energy of breaker and cable value k=115 Maximum prospective 2 4 5 6 10 15 20 25 30 36 50 65 70 100 fault level in kA MCBs SQO 3/6A 1 1 1 1 - - - - - - - - - - SQO 10A 1 1.5 1.5 1.5 - - - - - - - - - - SQO 16/20/25A 1 1.5 1.5 1.5 - - - - - - - - - - SQO 32/40A 1 1.5 1.5 2.5 - - - - - - - - - - SQO 50/63A 1.5 1.5 2.5 2.5 - - - - - - - - - - KQ 6A 1 1 1 1 1 1.5 - - - - - - - - KQ 10A 1 1.5 1.5 1.5 2.5 2.5 - - - - - - - - KQ 16/20/25A 1 1.5 1.5 1.5 2.5 2.5 - - - - - - - - KQ 32/40A 1 2.5 2.5 2.5 2.5 2.5 - - - - - - - - KQ 50/63A 1.5 2.5 2.5 2.5 2.5 4 - - - - - - - - KQ 80A 1.5 2.5 2.5 2.5 4 4 - - - - - - - - KQ 100A 2.5 2.5 2.5 4 4 4 - - - - - - - - MCCBs CDAE/CDLE up to 100A 6 6 6 6 6 6 6 6 - - - - - - CNAE/CNLE up to 250A 10 10 10 10 10 10 10 10 10 10 - - - - CHAE/CHLE up to 250A 10 10 10 10 10 10 10 10 10 10 10 - - - SLA/SLAL up to 400A 16 16 16 35 35 35 35 50 50 50 - - - - DHLE up to 630A 16 16 16 16 16 16 16 16 16 16 16 - - - LI/LCL/LIL up to 600A 10 10 10 10 10 10 16 16 16 16 16 16 16 16 SNA/SNAL up to 1250 50 50 50 50 50 50 50 70 70 70 70 - - - SMA/SMAL/SMHL up to 1000A 25 25 25 25 25 25 25 35 35 70 70 - - - PA/SPA/SPH up to 2000A 50 50 50 50 50 50 50 70 70 70 70 - - - Table 31 Current limiting circuit breakers let through less energy, therefore the cable sizes are not an indication of continuous current ratings. SQD5727 Electrical App. Sec 2 10/8/05 10:09 pm Page 25
Sec2 27 Commercial and industrial solutions for 3 phase distribution Cascading - Square D MCCB/MCB 2 Cascading chart Cascading permits the installation of a circuit breaker having a breaking capacity lower than the prospective at its point of installation. The upstream breaker, which must have the required breaking capacity, limits the fault current to that which may safely be interrupted by the downstream breaker. In the case of a high fault current both breakers may operate. For example: a LoadCentre KQ breaker rated at 10kA may be used at a point in the network having a prospective fault current of 40kA provided that it is protected by a CH breaker rated 100A (50kA). Upstream breaker Downstream breaker Ref Rating Icu 6kA 6kA 10kA 25kA 36kA 36kA CD 100A 25kA 25 25 25 CN 100A 36kA 25 25 25 36 CN 250A 36kA 30 36 CH 100A 50kA 40 50 50 CH 250A 50kA 30 50 50 SLA 400A 36kA 36 DH 630A 50kA 50 50 SMAL 1000A 50kA 36 50 50 SPAF 2000A 50kA 36 50 50 Reference SQO DOM KQ CD CN SLA Rating 3 - 63A 3 - 50A 3 - 63A 100A 250A 400A Table 32 SQD5727 Electrical App. Sec 2 10/8/05 10:09 pm Page 27
Sec2 39 Commercial and industrial solutions for 3 phase distribution LoadCentre KQ industrial MCB performance figures 2 Type B MCBs Rating (A) Zs ohm @ 230V ac R2 5s 0.4s ohms 3 15 15 3.33 6 8 8 1.67 10 5 5 1.00 16 3 3 0.63 20 2.3 2.3 0.50 25 1.8 1.8 0.40 32 1.4 1.4 0.31 40 1.2 1.2 0.25 50 0.9 0.9 0.20 63 0.73 0.73 0.16 Type C MCBs Rating (A) Zs ohm @ 230V ac R2 5s 0.4s ohms 6 8 4 1.67 10 5 2.3 1.00 16 3 1.4 0.63 20 2.3 1.2 0.50 25 1.8 0.9 0.40 32 1.4 0.7 0.31 40 1.2 0.6 0.25 50 0.9 0.5 0.20 63 0.73 0.37 0.16 Table 47 Earth loop impedance values. Type D MCBs Rating (A) Zs ohm @ 230V ac R2 5s 0.4s ohms 6 8 2.7 1.67 10 5 1.6 1.00 16 3 1.0 0.63 20 2.3 0.8 0.50 25 1.8 0.7 0.40 32 1.4 0.5 0.31 40 1.2 0.4 0.25 50 0.9 0.3 0.20 63 0.73 0.26 0.16 Type C 80 and 100A MCBs Rating (A) Zs ohm @ 230V ac R2 5s 0.4s ohms 80 0.58 0.29 0.13 100 0.46 0.23 0.10 Table 48 SQD5727 Electrical App. Sec 2 10/8/05 10:09 pm Page 39

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sqd-app-guide-2-25c.pdf

  • 1. Sec2 25 Commercial and industrial solutions for 3 phase distribution Energy let through 2 I2 t Energy let through The energy let through by a breaker determines the minimum size of the downstream cable. Minimum cable size required based on I2 t let through energy of breaker and cable value k=115 Maximum prospective 2 4 5 6 10 15 20 25 30 36 50 65 70 100 fault level in kA MCBs SQO 3/6A 1 1 1 1 - - - - - - - - - - SQO 10A 1 1.5 1.5 1.5 - - - - - - - - - - SQO 16/20/25A 1 1.5 1.5 1.5 - - - - - - - - - - SQO 32/40A 1 1.5 1.5 2.5 - - - - - - - - - - SQO 50/63A 1.5 1.5 2.5 2.5 - - - - - - - - - - KQ 6A 1 1 1 1 1 1.5 - - - - - - - - KQ 10A 1 1.5 1.5 1.5 2.5 2.5 - - - - - - - - KQ 16/20/25A 1 1.5 1.5 1.5 2.5 2.5 - - - - - - - - KQ 32/40A 1 2.5 2.5 2.5 2.5 2.5 - - - - - - - - KQ 50/63A 1.5 2.5 2.5 2.5 2.5 4 - - - - - - - - KQ 80A 1.5 2.5 2.5 2.5 4 4 - - - - - - - - KQ 100A 2.5 2.5 2.5 4 4 4 - - - - - - - - MCCBs CDAE/CDLE up to 100A 6 6 6 6 6 6 6 6 - - - - - - CNAE/CNLE up to 250A 10 10 10 10 10 10 10 10 10 10 - - - - CHAE/CHLE up to 250A 10 10 10 10 10 10 10 10 10 10 10 - - - SLA/SLAL up to 400A 16 16 16 35 35 35 35 50 50 50 - - - - DHLE up to 630A 16 16 16 16 16 16 16 16 16 16 16 - - - LI/LCL/LIL up to 600A 10 10 10 10 10 10 16 16 16 16 16 16 16 16 SNA/SNAL up to 1250 50 50 50 50 50 50 50 70 70 70 70 - - - SMA/SMAL/SMHL up to 1000A 25 25 25 25 25 25 25 35 35 70 70 - - - PA/SPA/SPH up to 2000A 50 50 50 50 50 50 50 70 70 70 70 - - - Table 31 Current limiting circuit breakers let through less energy, therefore the cable sizes are not an indication of continuous current ratings. SQD5727 Electrical App. Sec 2 10/8/05 10:09 pm Page 25
  • 2. Sec2 27 Commercial and industrial solutions for 3 phase distribution Cascading - Square D MCCB/MCB 2 Cascading chart Cascading permits the installation of a circuit breaker having a breaking capacity lower than the prospective at its point of installation. The upstream breaker, which must have the required breaking capacity, limits the fault current to that which may safely be interrupted by the downstream breaker. In the case of a high fault current both breakers may operate. For example: a LoadCentre KQ breaker rated at 10kA may be used at a point in the network having a prospective fault current of 40kA provided that it is protected by a CH breaker rated 100A (50kA). Upstream breaker Downstream breaker Ref Rating Icu 6kA 6kA 10kA 25kA 36kA 36kA CD 100A 25kA 25 25 25 CN 100A 36kA 25 25 25 36 CN 250A 36kA 30 36 CH 100A 50kA 40 50 50 CH 250A 50kA 30 50 50 SLA 400A 36kA 36 DH 630A 50kA 50 50 SMAL 1000A 50kA 36 50 50 SPAF 2000A 50kA 36 50 50 Reference SQO DOM KQ CD CN SLA Rating 3 - 63A 3 - 50A 3 - 63A 100A 250A 400A Table 32 SQD5727 Electrical App. Sec 2 10/8/05 10:09 pm Page 27
  • 3. Sec2 39 Commercial and industrial solutions for 3 phase distribution LoadCentre KQ industrial MCB performance figures 2 Type B MCBs Rating (A) Zs ohm @ 230V ac R2 5s 0.4s ohms 3 15 15 3.33 6 8 8 1.67 10 5 5 1.00 16 3 3 0.63 20 2.3 2.3 0.50 25 1.8 1.8 0.40 32 1.4 1.4 0.31 40 1.2 1.2 0.25 50 0.9 0.9 0.20 63 0.73 0.73 0.16 Type C MCBs Rating (A) Zs ohm @ 230V ac R2 5s 0.4s ohms 6 8 4 1.67 10 5 2.3 1.00 16 3 1.4 0.63 20 2.3 1.2 0.50 25 1.8 0.9 0.40 32 1.4 0.7 0.31 40 1.2 0.6 0.25 50 0.9 0.5 0.20 63 0.73 0.37 0.16 Table 47 Earth loop impedance values. Type D MCBs Rating (A) Zs ohm @ 230V ac R2 5s 0.4s ohms 6 8 2.7 1.67 10 5 1.6 1.00 16 3 1.0 0.63 20 2.3 0.8 0.50 25 1.8 0.7 0.40 32 1.4 0.5 0.31 40 1.2 0.4 0.25 50 0.9 0.3 0.20 63 0.73 0.26 0.16 Type C 80 and 100A MCBs Rating (A) Zs ohm @ 230V ac R2 5s 0.4s ohms 80 0.58 0.29 0.13 100 0.46 0.23 0.10 Table 48 SQD5727 Electrical App. Sec 2 10/8/05 10:09 pm Page 39