Consider the following statements regarding Preventive Maintenance of industrial electrical systems:1.Thermography is used to detect "hot spots" in electrical connections and panels.2.Measurement of Earth Resistance should be done periodically using an Earth Tester.3.Dielectric strength testing is performed only on cables and never on transformer oil.Which of the statements given above is/are correct?
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Preventive maintenance aims to detect deterioration before failure. Electrical programs combine thermal inspection, insulation testing, earth-continuity/resistance checks, contact tightening, protection testing and oil diagnostics where applicable. Key relation: Thermal principle: abnormal I²R heating reveals high-resistance connections. Dielectric-strength tests determine the electric stress at which insulation breaks down under the specified test method.
Exam focus: Thermography = hot spots; earth tester = grounding health; BDV test = transformer oil insulation quality. Common trap: Believing dielectric testing applies only to solid cable insulation.
Formula / Key Relation
Thermal principle: abnormal I²R heating reveals high-resistance connections. Dielectric-strength tests determine the electric stress at which insulation breaks down under the specified test method.
Detailed Explanation
Correct Answer: A - 1 and 2 only Quick Concept Explanation Preventive maintenance aims to detect deterioration before failure. Electrical programs combine thermal inspection, insulation testing, earth-continuity/resistance checks, contact tightening, protection testing and oil diagnostics where applicable. Key relation: Thermal principle: abnormal I²R heating reveals high-resistance connections. Dielectric-strength tests determine the electric stress at which insulation breaks down under the specified test method.Exam focus: Thermography = hot spots; earth tester = grounding health; BDV test = transformer oil insulation quality. Common trap: Believing dielectric testing applies only to solid cable insulation. Statement-wise Verification Statement 1 - Correct.Thermography is used to…
Correct Answer: A - 1 and 2 only
Quick Concept Explanation
Preventive maintenance aims to detect deterioration before failure. Electrical programs combine thermal inspection, insulation testing, earth-continuity/resistance checks, contact tightening, protection testing and oil diagnostics where applicable. Key relation: Thermal principle: abnormal I²R heating reveals high-resistance connections. Dielectric-strength tests determine the electric stress at which insulation breaks down under the specified test method.
Exam focus: Thermography = hot spots; earth tester = grounding health; BDV test = transformer oil insulation quality. Common trap: Believing dielectric testing applies only to solid cable insulation.
Statement-wise Verification
Statement 1 - Correct. Thermography is used to detect "hot spots" in electrical connections and panels. Thermography identifies temperature rise caused by loose joints, overload, imbalance, poor contacts and other high-resistance defects without shutting equipment down in many cases.
Statement 2 - Correct. Measurement of Earth Resistance should be done periodically using an Earth Tester. Earth-electrode/earthing-system resistance is checked periodically with suitable earth-resistance test methods/instruments as part of electrical safety maintenance.
Statement 3 - Incorrect. Dielectric strength testing is performed only on cables and never on transformer oil. Breakdown-voltage/dielectric-strength testing is a standard condition test for transformer insulating oil as well as for other insulation systems.
Core Concept
Preventive maintenance aims to detect deterioration before failure. Electrical programs combine thermal inspection, insulation testing, earth-continuity/resistance checks, contact tightening, protection testing and oil diagnostics where applicable.
Formula / Key Relationship
Thermal principle: abnormal I²R heating reveals high-resistance connections. Dielectric-strength tests determine the electric stress at which insulation breaks down under the specified test method.
Step-by-Step Check
Established maintenance practices confirm 1 and 2. Transformer-oil dielectric testing provides a direct counterexample to statement 3. Option A.
Why the Other Options Are Wrong
Option B is incorrect because it includes incorrect statement(s) 3 and omits correct statement(s) 1. Option C is incorrect because it includes incorrect statement(s) 3 and omits correct statement(s) 2. Option D is incorrect because it includes incorrect statement(s) 3.
Answer-Key Verification Note
The uploaded provisional key marks C . After independent technical verification, the defensible answer is A . This discrepancy is stated explicitly rather than silently copying the provisional key.
Exam Shortcut / Approach
Thermography = hot spots; earth tester = grounding health; BDV test = transformer oil insulation quality.
Common Mistake
Believing dielectric testing applies only to solid cable insulation.
Quick Revision
Thermography Earthing and Dielectric Tests is linked with Preventive Maintenance, Maintenance and Industrial Electrical Systems. Thermography = hot spots; earth tester = grounding health; BDV test = transformer oil insulation quality.
Quick Trick
Thermography = hot spots; earth tester = grounding health; BDV test = transformer oil insulation quality.
Why Other Options Are Wrong
Option B is incorrect because it includes incorrect statement(s) 3 and omits correct statement(s) 1. Option C is incorrect because it includes incorrect statement(s) 3 and omits correct statement(s) 2. Option D is incorrect because it includes incorrect statement(s) 3.
Common Mistake
Believing dielectric testing applies only to solid cable insulation.
Exam Tip
Thermography = hot spots; earth tester = grounding health; BDV test = transformer oil insulation quality.
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