Class 12 Power Chapter 2 Maintenance of the Cable System

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Class 12 Power Chapter 2 Maintenance of the Cable System

Also, you can read the NCERT book online in these sections Solutions by Expert Teachers as per Central Board of Secondary Education (CBSE) Book guidelines. AHSEC Class 12 Elective Electrical Power System Textual Solutions are part of All Subject Solutions. Here we have given AHSEC Class 12 Electrical Power System Textbook Solutions English Medium for All Chapters, You can practice these here.

Maintenance of the Cable System

Chapter: 2

SESSION 1: LAYING OF UNDERGROUND CABLE

Exercise

A. Fill in the blanks with Suitable answers. 

1. ____________ is used for branching of a service cable from a main cable.

Ans: T-Joints.

2. Three faults that cables are tested for are _________, discontinuity and earth fault. 

Ans: Short circuiting.

3. __________. are overhead power lines using several insulated phase conductors, contrasting with the traditional practice of using un-insulated conductors separated by air gaps.

Ans: Aerial Bundled Cables (ABC).

B. Choose the correct answer from the following options. 

1. Mid – span joining should be avoided in the case of HT lines.

(a) True.

(b) False.

Ans: (a) True.

2. Which of these are disadvantages of AB Cables (you can choose more than 1): 

(a) Additional cost.

(b) Electricity theft is easy from these cables.

(c) Increased weight.

(d) Cluttered appearance. 

Ans: (a) Additional cost.

(c) Increased weight.

(d) Cluttered appearance.

4. Laying the cables is important for power distribution. So, no clearances are required.

(a) True.

(b) False.

Ans: (b) False.

C. Match the elements of Group A with Group B.

Group A	Group B
1. A cable test	(a) Yarlay Loop Test
2. This test is used to locate the fault of the long length of Cables.	(b) AB cables
3. Short spans, more poles Needed	(c) Murray Loop Test

Ans: 

Group A	Group B
1. A cable test	(c) Murray Loop Test
2. This test is used to  locate the fault of the long length of Cables.	(a) Yarlay Loop Test
3. Short spans, more poles Needed	(b) AB cables

D. Answer the following:

(a) Classify various types of cables.

Ans: Types of cables are classified in different ways such as based on their use, voltage and type of insulation used for their construction.

(i) PVC (Poly Vinyl Carbide Cable).

(ii) PILCA (Paper Insulated Lead Covered Armoured Cable).

(iii) XLPE (Cross Linked Poly Ethylene Cable).

(b) List tools and equipment used in cable laying activities.

Ans: 11 kV cable laying from cables drums using erection stools & pulling pulleys.

Other tools for cable laying are: Cable pulling winch, Cable guiding device and Cable pulling grip etc.

SESSION 2: LAYING OF AB CABLES

CHECK YOUR KNOWLEDGE

A. Tick the correct answer: 

1. Aerial Bundled Cables are the same as bundle conductors.

(a) False.

(b) True.

Ans: (a) False.

2. Cable joints should be near the support.

(a) False.

(b) True.

Ans: (b) True.

3. Messenger wire is not used as earth wire. 

(a) False.

(b) True.

Ans: (a) False.

4. Write short note on the following :

(a) Jointing of ABC cable.

Ans: Mid-span jointing is allowed in LT ABC systems but recommended to be at the supports. Mid-span jointing is not recommended for HT lines. If unavoidable, tapping at support points through suitable clamp connectors may be allowed. Conducting screen continuity must be maintained, and 3-phase screens may be earthed through surge arrestors.

(b) Types of AB cables.

Ans: (i) LT Lines:

Three Phase Four Wire: 3×150mm² + 1×95mm² (neutral) + messenger wire of 25mm².

Three Phase Five Wire (for street light): 3×150mm² + 1×95mm² + messenger wire 25mm² + 1×16/25mm² (street light).

Other type: 3×95mm² + 1×50mm² + messenger wire 25mm².

(ii) HT Lines (11kV):

3×150mm² + messenger wire 25mm²

3×95mm² + messenger wire 25mm²

B. Explain the following:

(a)  Explain the importance of various cable joints. 

Ans: Cable joints are essential to connect or extend cables safely and maintain electrical continuity. Proper jointing at support points ensures minimal stress, avoids mid-span failures, and maintains insulation and conductor integrity in both LT and HT lines.

(b) List the advantages of aerial bundled cables.

Ans: Advantages of Aerial Bundled Cables:

(i) Relative immunity to short circuits.

(ii) Safe near trees—no sparking if touched.

(iii) Simpler installation (no insulators/crossbars).

(iv) Less cluttered appearance.

(v) Requires narrower right-of-way.

(vi) Fewer splices at junction poles.

(vii) Increased safety against neutral break.

(viii) Electricity theft is harder and easily detectable.

SESSION 3: CONDUCTOR JOINTING

Exercises

SESSION 4: CABLE JOINTING

Exercise