Fault Current Limiting/Interrupting Solutions

Utility network operators are investing hundreds of millions of dollars in upgrading and replacing existing equipment. They often have no choice other than segmenting the grid which negatively impacts the quality and availability of their network. Independent power producers are required to make significant investments and bear long delays, before receiving permits to connect distributed generation and renewable sources.

GridON is offering grid operators, Independent Power Producers (IPP) and industrial customers cost-effective fault current limiting/interrupting solutions which enable increased power capacity in meshed networks, and cost-effective connection of Distributed Generation (DG) and renewable energy sources - while improving power quality and network stability.

GridON offers solutions for all power and voltage levels: a power-electronics Fault Current Limiting Interrupter (FCLi) for low-to-medium voltage connection of distributed generation and renewable sources; and a saturated core Fault Current Limiter (FCL) for medium-to-high voltage distribution and transmission networks. GridON's FCL/FCLi limit and interrupt fault currents from propagating through the network, thus preventing power failures and network outages. These cost-effective solutions significantly reduce capital expenditure and time consuming labor, required for conventional network upgrades.

Power-electronics Fault Current Limiting Interrupter (FCLi)

The FCLi is a series-connected solid-state based device which interrupts network current and limits transient voltages to acceptable levels, instantly upon detection of short circuit conditions. The FCLi is using a proprietary detection algorithm to sense faults. It then limits and interrupts excessive fault infeed from the generator to the grid within microseconds, long before the first current peak. The FCLi also protects private generators from fault currents which flow in their direction, and can rapidly disconnect the generator upon loss of mains. Once the short-circuit condition is cleared, the FCLi will immediately resumes to its normal conducting state. The use of power electronics enables fast recovery and return to service after each interruption operation, within seconds.

As fault current breaking elements, the solid-state based FCLi is using off-the-shelf power electronic devices (IGBT) that have accumulated extensive experience in commercial power systems. The FCLi was successfully tested at KEMA Labs, where it was subjected to multiple prospective fault currents – phase-to-earth, phase-to-phase and three-phase up to 25kA RMS, and fully interrupted the currents well before the first peak. The FCLi has undergone extensive factory acceptance tests such as functional tests, temperature rise tests and dielectric tests including lightning impulse test at 95kV. The FCLi technology is patent pending.

Using FCLi to connect a 5MW generator at 11kV

Using initially the highly coveted European Commission Horizon 2020 grant, GridON developed a power-electronics based solution - a relatively small and affordable product line for connecting Distributed Generation and Renewable Energy sources. The FCLi is a perfect solution for cost-effective connection of distributed private generators and for acquiring excess cogeneration supply from commercial and industrial plants. Return on investment in an FCLi is expected within less than one year. The FCLi is commercially available and has been operating flawlessly in public networks.

Power-electronics Fault Current Limiter Diverter (FCLd)

The FCLd (currently in development) is a power-electronics based solution which enables the connection of substation sections and increased supply capacity in the substation and its surrounding network. It also enables mass deployment of distributed generation and renewable energy sources. The FCLd provides solutions for networks up to 38kV.

When a short circuit condition is detected, the solid-state devices are used to create a diverting path for most of the current rather than interrupting it, limiting the fault current contribution to the network within equipment ratings. The proprietary fault detection mechanism is configurable and flexible, allows for maintaining the selectivity of the protection equipment. This enables implementation for high voltage and power rating, operating at negligible losses, and enabling immediate recovery when the fault condition is cleared. The FCLd is easy to operate and it does not require any part replacement or site presence.

Enabling increased power supply in a distribution substation:

By mitigating the fault current contribution from one or more transformers in the substation, the utility is able to connect multiple transformers and approve connection of additional private generation capacity, while ensuring that prospective fault current will always be kept within the network protection limits. Without the FCLd, the fault level exceeds the equipment ratings when the bus-tie circuit breaker is closed, and/or when the private generation is in operation. With the FCLd in operation, it will limit the fault current contribution from the transformer to the downstream equipment, allowing safe operation within the equipment ratings.

Enabling connection of generator sets into high voltage networks:

a single FCLd protects the 33kV network from fault current contribution from 6 LV generators. Without FCLd, the connection of the generator sets will drive the fault current beyond the 33kV substation equipment ratings. With an FCLd, the fault current contribution from the generator sets is significantly limited, allowing the 33kV substation to operate within its equipment ratings.

Saturated-core Fault Current Limiter (FCL)

The FCL is a passive, self-triggered system – imposing high impedance during fault condition. The FCL combines proprietary concept of electromagnetic flux alteration on a saturated core with conventional power transformer technology. The proprietary concept is utilizing the non-linear magnetic characteristic of iron core to introduce very high impedance to the grid during fault conditions. The unique geometry of the FCL enables significant increase of impedance during fault, providing ample current limiting. The FCL technology was granted several patents.

The FCL’s variable-impedance system responds instantaneously to current spikes long before the first peak, suppresses fault current for its entire duration, and recovers immediately following fault clearance – being always ready for consecutive faults.

Using FCL to enable connection of 4 parallel transformers

Being scalable to very high voltage and power ratings, this commercial, fail-safe product is well-suited for transmission and distribution network applications. The “transformer-like” FCL systems are very robust and easy to install and maintain.

The development of GridON’s legacy FCL was funded by a consortium of the UK Government and global industries (EDF, E.ON, Rolls-Royce, Caterpillar, BP and Shell). It was then adopted as a commercial, business-as-usual solution by a number of network operators, including UK Power Networks and Western Power Distribution, proving very reliable and effective in limiting numerous fault current events.

Typical applications

FCLi enables cost-effective connection of distributed generators and low carbon energy sources from IPPs and industrial/commercial generators into low-medium voltage networks. It enables sale of excess generation capacity to the grid.	FCL/FCLi on a transformer feeder enables paralleling of multiple transformers on a single connected bus, reducing the overall substation fault levels to be within switchgear ratings.	FCL/FCLi in a bus-tie location enables paralleling bus sections during loss of power sources, improving network interconnectivity and power quality.

Please complete the request form in order to learn more about our FCL/FCLi solutions and their capabilities.