The incoming compartment, where power is connected to the harmonic filter bank, is normally configured based on the availability of existing breakers, disconnect switches, and the rating of the filter bank. Typical configurations options are provided below.

ACCESSORIES FOR INCOMING COMPARTMENT

The following items are available for placement in the incoming compartment.

The capacitor compartment may consists of one filter bank or multiple capacitor stages. A filter bank or stage normally consists of the capacitors, capacitor fuses, and where applicable, a switching device and inrush reactors. Typical bank or stage configuration options are provided below. The filter bank/stage compartment is compartmentalized and isolated from the incoming compartment to allow for maintenance and repair.

The harmonic filter bank can be connected in a number of different ways depending upon bank rating and protection requirements. Typically, filter banks are provided with an ungrounded wye or ungrounded split-wye connection, but a grounded wye and Delta connection are also available.

Air Disconnect Switch
Externally operated chain-drive operated 3-pole air-disconnect switch to provide a "visible-break" and electrical isolation of the harmonic filter bank during maintenance and repair.

Ground Switch
Externally operated chain-drive or direct-drive operated 3-pole ground switch to ground the load-side terminals of the incoming air-disconnect switch, breaker, and/or capacitors for safety during maintenance. The ground switch is key interlocked with the upstream disconnecting device to prevent closing of the ground switch onto a live bus.

Main Incoming Fuses
Main incoming current limiting fuses (with local and remote blown fuse indication) for short circuit protection of the harmonic filter bank.

Main Incoming Breaker
Main incoming drawout or fixed-mounted circuit breaker for protection, isolation, and switching of the harmonic filter bank.

Lightning Arresters
Lightning arresters are provided as standard to protect the harmonic filter bank and incoming cables from lightning and switching transients.

Control Power Transformer(s) (CPT)
Control power transformers to supply control power and voltage sensing to the filter bank's, metering, protection, and control system.

Current Transformers (CT)
Current tranformers to supply a current signal for the filter bank's metering, protection, and control system.

Bus Duct Entry
Bus duct entry to allow for direct bus connection to switchgear.

Dead-Front Entry
Dead-front design entry that allows for 200 amp and 600 amp separable elbow connectors.

Roof Bushing Entry
Roof bushing entry to allow for direct connection to overhead bus within substations.

Capacitors
Low loss, double bushing capacitors that meet or exceed IEC 871, IEEE 18 and CSA standards. Capacitors are typically connected ungrounded-wye or ungrounded split-wye. Internal discharge resistors reduce the residual voltage to less than 50 volts within 5 minutes of de-energization. The dielectric fluid is environmentally friendly, biodegradable, non PCB, with low toxicity. Internally fused capacitors are available upon request.

Capacitor Fusing
Capacitors are individually fused with current limiting fuses. These fuses reduce the possibility of case rupter on capacitor failure and allow the harmonic filter bank to continue to operate when a capacitor fails. The fuses are equipped with blown fuse indicators and can also be equipped with direct fuse operation sensors for blown fuse detection.

Capacitor Switches
Single stage and multi-stage harmonic filter banks are equipped with vacuum contactors (for voltages less than 6.6kV), capacitor switches, or circuit breakers (fixed or drawout) for capacitor switching.

Iron Core Filter Reactors
Iron-core filter reactors provide the necessary inductance (inductive reactance) to tune the capacitor bank to the desired frequency. In addition to tuning, the reactors significantly reduce the frequency and magnitude of inrush currents from back-to-back capacitor bank switching.

High Pass Filter Resistors
Stainless steel Grid Reistors are provided for C-High Pass, High-Pass, and Double-Tuned Harmonic Filters. Resistors are of a stainless steel stamped grid design that offer compact high wattage capability, low temperature coefficient, and corrosion resistance.

Current Transformers
Multi-stage or multi-tuned harmonic filter banks can be equipped with current transformers to provide a current signal for metering and protection. Current transformers can be provide to monitor both iron-core reactor current as well as high-pass resistor current.

Air Disconnect Switch
Externally operated, key interlocked, 3-pole air-disconnect switch(s) that isolates a single stage of a multi-stage filter bank, allowing for partial bank operation during maintenance.

Ground Switch
Externally operated, key interlocked, 3-pole ground switch(s) that grounds the capacitor terminals to ensure all trapped charge has been removed from the capacitors.

Automatic Filter Bank Controllers
Automatic harmonic filter Banks are equipped with various types of controllers to automatically turn harmonic filter banks (stages) on and off based on var flow, power factor, harmonic distortion, watt flow, voltage level, current-flow, time-of-day, or day-of-week. Controllers are integrated with the protection system and other components to form a fully integrated system.

Protection
Harmonic filter Banks can be equipped with various protection relays, meters, and sensors to protect the filter bank as well as the system from over-voltage, out-of-balance operation from capacitor failure, internal faults and over-temperature due to fan failure. Protection devices are integrated with the control system and other components to form a fully integrated system.

Arc Flash Mitigation
See NEPSI’s technical note on arc flash mitigation in metal-enclosed capacitor banks and harmonic filter banks. This technical note provides over 30 mitigation strategies available from NEPSI to minimize the level of exposure to arc flash events as well as ways to reduce the probability that an arc flash event will occur in the first place.

Enclosure
Free standing, compartmentalized, all welded, 11 gauge galvanneal steel construction with 3 point pad-lockable latching handles and stainless steel hinges. The enclosure is painted with Engineered Siloxane, a Marine paint with rated salt spray of 5500 hours. NEMA 3R (IP64) construction is standard, NEMA 12 (IP65) and 4X (IP66) are available as an option. Base of enclosure as well as capacitor supports are formed from C4 structural steel. Door stays and windows are standard.

Key Interlock System
Key interlock system are available that dictate sequence of operation and safe entry into the enclosure. Upstream devices may be included in the interlock sequence.

Ground and Phase Bus
A 1/4" X 2" Tin plated ground bus is provided through the width of the enclosure to assist in grounding during maintenance. All phase bus is Tin plated square edged and rated at a minimum of 135% of the bank nominal current rating.