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MV CAPACITOR BANKS (with HARMONIC FILTERS)


Metal-Enclosed or ISO Container-Enclosed

 

 

Standards: IEEE Std. 1036, IEC 60871-1

 

 

Capacitor Bank Tests
  • Coating thickness measurement
  • Capacitance measurement
  • Power frequency withstand test
  • Insulation resistance measurement
  • Full capacity loading test
  • Lightning impulse test
  • Consult factory for other tests
Introduction
  • Stand-alone complete system with ease of installation
  • Includes earthing switch to disconnect feeder & earth capacitors
  • Includes three phase iron-core/air-core harmonic filter reactors or air-core inrush current limiting reactors
  • Optional high pass low inductance resistors
  • Vacuum contactors to switch capacitors
  • Capacitor fuses included
  • Automatic power factor correction controller included
  • Over-voltage relay, over-current relay, CTs and VTs included
  • Robust structure against corrosion, direct sunlight, rain and harsh environmental conditions
  • Touch protections included for safety
  • 2.4 kV - 36 kV 50-60 Hz, BIL 200 kV
  • Double star connection for unbalanced loading
  • Optional smoke detector
  • Indoor/outdoor modular structure
  • Flexible and expendable structure

 

Areas of Use
  • Power factor correction
  • Harmonic Filtering
  • Over-voltage protection
  • Loss mitigation

 

Capacitor Battery Tests
  • 4V_n (DC) 10 sec. or 2V_n (AC) 10 sec. between terminals,
  • tan⁡(δ) (loss angle) measurement
  • Capacitance measurement
  • Leakage test
Capacitor Bank Protections

The current of the protection fuses should be selected as If≅2In.

51 relay should be set with a delay for 0.1 seconds between 4-6In (short circuit protection)

50 relay should be set with a delay for 4 seconds for 1.3In (overload protection)

50N relay is recommended to be set with a delay for 4 seconds at the setting of 0.05In (overload protection)

The value of resistor R (kΩ) required to be connected across the capacitor to drop the voltage of the capacitor battery with a capacitance of C (μF) to under 75 V after 10 minutes (600 seconds), can be calculated as below:

 

For Delta connection

For Delta connection


For Star connection

For Star connection


 

U:System voltage (V)

In: Capacitor nominal current (A)

Inrush Current (I_C) Calculation When a Single Battery is Connected to the Circuit
  • - U: Phase-Neutral voltage (V)
  • - Xc: Phase-Neutral capacitive reactance (Ω)
  • - XL: Total inductive reactance between batteries (Ω)
  • - Q; Q_1; Q_2: Battery powers (kVAr)
  • - S_SC: Short circuit power (kVA) at the point where the capacitors are connected
  • - I_N : Nominal current (A_rms) of the battery.
  • - I_SC : Short circuit current (A_rms) at the point where the capacitor bank is connected.

 

The value of the inductor to be connected in series with the capacitor to limit the inrush current down to I_C ≤100I_N:

Inrush Current


Inductor Value


Inrush Current (I_C) Calculation When (n) Number of Capacitor Batteries are Connected in Parallel:

 

Inrush current (IC) when a capacitor battery is connected in parallel with an energized capacitor battery

 

 

Calculations Related to Capacitor Banks:

In capacitors I_max=1.3 I_n

  • V_max=1.1 V_n - 12 hours / day
  • V_max=1.2 V_n - 5 min
  • V_max=1.3 V_n - 1 min

When a capacitor bank with a power of Q (kVAr) is connected to a system with a short circuit power of S_sc (kVA), the resonance frequency is:

 

  • S: Power (kVA) of the transformer supplying the capacitor
  • S_SC: Short circuit power (kVA) of the transformer supplying the capacitor
  • Z_SC: Short circuit impedance of the transformer supplying the capacitor (%)

Determining the Q_N of the capacitor required in order to provide a capacitive power of Q_s to a system with a voltage of (U_s):

Application Examples

Vacuum circuit breaker at entry

 

Disconnector switches for disconnecting and earthing the capacitors

 

Equipped with inrush reactor

 

CT for unbalance protection

 

Capacitor protection fuses

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