Wednesday 8 May 2019

Contractor’s Supervisor


Contractor’s Supervisor Personnel understands the owner/ Consultant HSE policy requirements and implement:
supervisor

• Organize work to the required safety standards to prevent injuries, damage to property and environment.
• Ensure all persons have undergone safety induction training before engaging the on the job.
• Prepare and implement only safe and approved work methods, instruct and ensure compliance by work force.
• Enforce and comply with all work permit procedures.
   Prior to assigning the days task inspect the work site, correct unsafe conditions if any and report to site management to prevent recurrence.
• Prepare Safe Plan of Action (SPA) and communicate the same to his workforce.
• Communicate and ensure all identified hazards and preventive measures related to the task are understood by the workforce.
• Ensure all required safety resources are available and in good condition.
• Inspect all scaffold, elevated platforms, fall and fire preventive/protective equipments involved in the task,
• Inspect all tools and equipments, safety guards, instruments are in good operating conditions.
• Ensure required Personal Protective Equipments are available.
• Plan and ensure a good housekeeping.
• Monitor and control the task for unsafe acts and conditions.
• Co ordinate task with other activities in the job site.
• Ensure awareness of Emergency procedures, First aid, Fire fighting etc among the workforce.
• Cooperate and implement instructions from Safety and Fire departments.

Saturday 4 May 2019

Earthing strip size and fault level typical


EQUIPMENT EARTHING
All the equipment should be grounded with double run earth strip directly connected to earth mat at two different points.  The table provides the guidelines for Selection of Cross section of Earth conductor as per IEEE 80-2000 Clause 11.3.1 Equation 37 & Mild Steel as an Earth Conductor.
earthing strip size

Sr.
Fault current Level (KA)
Minimum Required Area of Cross Section (Sq.mm)
1
5
54
2
10
108
3
15
163
4
20
217
5
25
271
6
30
325
7
35
379
8
40
433

For various Equipments such as Power Transformer, Station Transformer, 11 KV Switch gear, 415V Panel, Light panel, Junction box, Street Lighting pole, Metallic fence, Isolator, Gantry tower & Electronic Earthing different cross sections of Earth conductor shall be selected as per the fault level. For switch gear rooms, a local earth conductor of adequate size of G.I flat may be run around the room below floor level to facilitate earthing of equipments in switchgear room.

Tuesday 26 March 2019

Earthing strip matrix for transformer


Earthing strip size for transformer.
Cross Section Area of Earthing Conductor As per IS 3043
A = (If x√t) / K  
Where:
t = Fault current Time (Second)., 1 sec or 3 sec
K = Material Constant, Material Constant, For GI=80, copper K=206, Aluminium K=126).
Part-A: Typical Protective conductor size required for Transformer Ratings (100-500KVA)





Sr.
A
B
C
D
E
F
1
Transformer Rating ( KVA)
100
160
250
315
500
2
Secondary Voltage (V)
433
433
433
433
433
3
Full Load current
133
213
333
420
667
4
Percentage Impedance Z%
5
5
5
5
5
5
Short Circuit Current (SC) in A =FLC*(100/Impedance)
2660
4260
6600
8400
13340
6
Area of Protective conductor Reqd in sq.mm = SC *√t/k





7
t = 1 Sec





8
Copper k = 206
12.9
20.7
32.0
40.8
64.8
9
Recommended strip size
25 x 3 mm
25 x 3 mm
25 x 3 mm
25 x 3 mm
25 x 3 mm
10
Alluminium k = 126
21.1
33.8
52.4
66.67
105.9
11
Recommended strip size
25 x 3 mm
25 x 3 mm
25 x 3 mm
25 x 3 mm
25 x 6 mm
12
Steel, k= 80
33.3
53.3
82.5
105
166.8
13
Recommended strip size
25 x 3 mm
25 x 3 mm
25 x 6 mm
25 x 6 mm
40 x 6 mm
14
t =3 Sec





15
Copper k = 206
22.34
35.85
56.42
70.67
112.23
16
Recommended strip size
25 x 3 mm
25 x 3 mm
25 x 3 mm
25 x 3 mm
25 x 6 mm
17
Alluminium k = 126
36.55
58.54
90.76
115.47
183.42
18
Recommended strip size
25 x 3 mm
25 x 3 mm
25 x 6 mm
25 x 6 mm
40 x 6 mm
19
Steel , k= 80
57.68
92.32
142.89
181.86
288.9
20
Recommended strip size
25 x 3 mm
25 x 6 mm
25 x 6 mm
40 x 6 mm
50 x 6 mm

PART-B: Typical Protective conductor size required for Transformer Ratings (630-2000KVA)
Sr.
A
G
H
I
J
K
L
1
Transformer Rating ( KVA)
630
750
1000
1250
1600
2000
2
Secondary Voltage (V)
433
433
433
433
433
433
3
Full Load current
840
1000
1333
1667
2133
2667
4
Percentage Impedance Z%
5
5
5
6
6
6
5
Short Circuit Current (SC) in A
16801
20001
26668
27779
35558
44447
6
Area of Protective conductor Reqd in sq.mm = SC *√t/k






7
t = 1Sec






8
Copper k = 206
81.96
97.57
130.09
135.51
173.45
216.81
9
Recommended strip size
25 x 6 mm
25 x 6 mm
25 x 6 mm
25 x 6 mm
40 x 6 mm
40 x 6 mm
10
Alluminium k = 126
133.34
158.74
211.65
220.47
282.2
352.75
11
Recommended strip size
25 x 6 mm
40 x 6 mm
40 x 6 mm
40 x 6 mm
50 x 6 mm
75 x 6 mm
12
Steel, k= 80
210.01
250.01
333.35
347.24
444.47
555.59
13
Recommended strip size
40 x 6 mm
50 x 6 mm
75 x 6 mm
75 x 6 mm
75 x 6 mm
75 x10 mm
14
t =3 Sec






15
Copper k = 206
141.26
168.17
224.22
233.56
298.96
373.7
16
Recommended strip size
25 x 6 mm
40 x 6 mm
40 x 6 mm
40 x 6 mm
50 x 6 mm
75 x 6 mm
17
Alluminium k = 126
230.95
274.94
366.58
381.86
488.78
610.97
18
Recommended strip size
40 x 6 mm
50 x 6 mm
75 x 6 mm
75 x 6 mm
75 x 10 mm
75 x 10 mm
19
Steel , k= 80
363.74
433.03
577.37
601.42
769.82
962.28
20
Recommended strip size
75 x 6 mm
75 x 6 mm
75 x10 mm
75 x10 mm
100 x 10 mm
100 x 10 mm


Reader can choose safely factor as 1.5.
Suppose calculated strip size is 40x6 sqmm = 240sqmm
Considering safety factor , strip size = 240x1.5 = 360 sqmm.
Electrode always should be installed in 2 and opposte side of equipment. The distance between electrode is not less than height of one electrode.

One Nation, One electrical License

Electrical contractors are facing license problem when they bid for another state. Generally they are entitled to do work in particular stat...