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The secondary circuit of ct should be closed before the transformer energies.
True
False
True
The secondary circuit of a Current Transformer (CT) must always be closed, either through a burden or a short-circuiting link, before the primary circuit is energized. Leaving the secondary open-circuited while the primary carries current results in extremely high voltages, causing insulation failure and posing a lethal safety hazard.
The secondary circuit of a Current Transformer (CT) must always be closed, either through a burden or a short-circuiting link, before the primary circuit is energized. Leaving the secondary open-circuited while the primary carries current results in extremely high voltages, causing insulation failure and posing a lethal safety hazard.
e=Ndtd╧ХтАЛ тАФ Induced EMF in the secondary winding
ImagтАЛтЙИIpтАЛ тАФ When secondary is open, magnetizing current equals primary current
When a CT is energized with an open secondary, the secondary MMF vanishes, leaving the entire primary current to act as a magnetizing current. This drives the CT core into extreme saturation, producing a high-frequency, high-amplitude pulsating flux, which induces a dangerously high 'peaky' voltage across the secondary terminals based on Faraday's law of induction, e=тИТNdtd╧ХтАЛ.
An open-circuited CT secondary acts like a voltage source with very high impedance.
The peak voltage can exceed several kilovolts, leading to arcing or breakdown.
CTs are inherently current sources; they require a closed-loop path to maintain flux balance.
Always use shorting blocks or test switches for maintenance to avoid accidental open-circuiting.
Prevents insulation breakdown of the CT secondary winding.
Ensures safety of operating personnel from high-voltage electric shocks.
Prevents overheating and permanent degradation of the CT magnetic core.
Switchgear protection systems
Current metering circuits
Differential protection relays
The secondary of a CT is typically standardized to 1A or 5A ratings.
Option B (False) is incorrect because an open-circuited secondary creates an unstable and dangerous condition in the transformer and connected instrumentation.
A is correct тАФ The secondary circuit of a CT must remain closed to prevent the development of dangerously high voltages that could damage the insulation and pose safety risks.
In any CT operation, always 'short before you disconnect' and 'connect before you unshort' to maintain the secondary loop integrity.