; Grounding Design Problems
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# Grounding Design Problems

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```									Problems

1. A factory in the Philippines has the following generator sets:

Elements      X         X'd         X"d         Xo       Voltage      MVA   Remarks
%          %           %          %

G1                     18.00%       10.00%      3.50%     240.00 0.300

G2                     18.00%       10.00%      3.50%     240.00 0.300

G3                     25.00%       14.00%      5.80%     240.00 0.625

Design and/or specify the grounding reactor for each generator.

Line to ground
Gen       Voltage              voltage
Computed Eq. 1-Eq.
Ohmic Reactance      5
Current Rating       Use Sequence Network

One-line Diagram

Remark
Elements                        X     X'd      X"d       Xo   Voltage MVA      s
%      %        %        %
25.40    12.70     6.50
GT1 -GT4                                 %        %        % 13,800 29.600
26.00    13.00     7.00
GT5                                      %        %        % 13,800 10.000
Transformers - will
0.40
SYN BUS Reactors                                               13,800        ohms
Diesel generating sets are
to be retired.

REQUIREMENTS:

If grounding reactors for gas turbine generators GT1 to GT5 will be used,
find the appropriate reactances. Diesel generating sets are to be retired.
3.           Following are loads of main distribution board (MDB):

Load                              MDB is 3-phase, 3-w +N +gnd, 220/127 v.
Ckt.      Description
DP-1 is 3-ph;
No.
DP-2 is connected at phase AN.
1        DP-1: 250 KW, 0.8
DP-3 is connected at phase BN.
p.f lag ., 3-ph., 220 v
DP-4 is connected at phase CN
2        DP-2: 50 KW, unity
p.f , 1-phase, 127 v
Capacitor is 3-ph
DP-3: 250 KW,                              DP-5 is connected at phase BN
3        0.85                                       DP-6 is 3-ph
p.f lag , 1-phase,
127 v
DP-4: 200 KW,
4        0.80
p.f lag , 1-phase,
127 v
Capacitor: 3-ph, 220
5        v
Max KVAR:        125.00
DP-5: 225 KW,
6        0.80
p.f lag , 3-phase,
220 v

Draw the vector diagram showing ,phase voltage & phase currents.
Compute line currents, phase current, ground current.
Specify the circuit breakers.

4.          Describe and evaluate the existing grounding system in your work site.

5.           Discuss LVCB which have several function, including those with ground fault
protection.

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