Question

(c) As a new protection engineer, your as asked to configure the IDMT relay setting for the network and fault location as shown in Figure Q2(c). The relay information an setting is given in Table Q2(c)(i). Table Q2(c)(ii) shows the time-characteristics data for all the relays. The fault current value that you're investigating is for 1.5kA and the time grading setting for relay coordination is 600ms. Calculate the actual operating time of all the relays. Table Q2(c)(i) CT ratio R1 R2 R3 Relay pickup current 200/5A 200/5A 100/5A Time multiplier settings 5A 2.5A 2.5A unknown unknown 0.1 Table Q2(c)(ii) Plus Setting Multiplier 2 3 5 7.5 10 15 20 30 Operating time (sec) 10 6 4.5 3.5 3 2.4 2 1.5 Current flow CB1 CB2 CB3 G Line 1 Line 2 Line 3 R1 R2 R3 Figure Q2(c)

          (c) As a new protection engineer, your as asked to configure the IDMT relay setting for the network and fault location as shown in Figure Q2(c). The relay information an setting is given in Table Q2(c)(i). Table Q2(c)(ii) shows the time-characteristics data for all the relays. The fault current value that you're investigating is for 1.5kA and the time grading setting for relay coordination is 600ms. Calculate the actual operating time of all the relays.
Table Q2(c)(i)
CT ratio	R1	R2	R3
Relay pickup current	200/5A	200/5A	100/5A
Time multiplier settings	5A	2.5A	2.5A		unknown	unknown	0.1
Table Q2(c)(ii)
Plus Setting Multiplier	2	3	5	7.5	10	15	20	30
Operating time (sec)	10	6	4.5	3.5	3	2.4	2	1.5
Current flow
CB1	CB2	CB3
G	Line 1	Line 2	Line 3
R1	R2	R3
Figure Q2(c)

(c) As a new protection engineer, your as asked to configure the IDMT relay setting for the network and fault location as shown in Figure Q2(c). The relay information an setting is given in Table Q2(c)(i). Table Q2(c)(ii) shows the time-characteristics data for all the relays. The fault current value that you're investigating is for 1.5kA and the time grading setting for relay coordination is 600ms. Calculate the actual operating time of all the relays.
Table Q2(c)(i)
CT ratio R1 R2 R3
Relay pickup current 200/5A 200/5A 100/5A
Time multiplier settings 5A 2.5A 2.5A unknown unknown 0.1
Table Q2(c)(ii)
Plus Setting Multiplier 2 3 5 7.5 10 15 20 30
Operating time (sec) 10 6 4.5 3.5 3 2.4 2 1.5
Current flow
CB1 CB2 CB3
G Line 1 Line 2 Line 3
R1 R2 R3
Figure Q2(c)

Added by Todd C.

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