Is-Limiter

What is a high-capacity fast switching device

As shown within the dotted lines in Figure 1, a high-capacity fast switching device consist of a bridge FS, a fuse FU, a nonlinear resistor FR, and a testing and control unit CT.  

Bridge

    Under normal circumstances, the bridge has the eectric current flow through it. In case of a short circuit, the bridge disconnects quickly within 0.15 ms.

Fuse

   The short circuit current is diverted to The fuse upon the bridge's disconnection.

It fuses within 0.5 ms and produces an adequate arc pressure.

Nonlinear resistor

   The arc pressure produced by fusing absorbs the magnetic field and limits the overvoltage occurring at the disconnection within an allowable level.

Testing and control unit

   This unit monitors the electric current and its rate of change. It sends a disconnecting signal to the bridge in case of malfunction.

 Features of high-capacity fast switching device

Due to its new principle, advanced technology and fine design, the high-capacity fast switching device is superior to a conventional protector with a breaker plus a relay.

20 times faster

   The failure current is broken within 1 ms and drops to 0 within 3 ms, and the failure is completely eliminated.

   The conventional protector with a breaker Plus a relay would take at least 60 ms to break a failure current.

 Higher sensitivity with current's rate of change closely monitored When a failure current occurs, an increased rate of change is shown.

Optimal design and higher reliability

   When a current has its amplitude and rate of change exceed the normal values at the same time, it is judged a short circuit.

   The three identical independent testing and control elements will judge a failure based on their "votes", and set off a disconnecting signal without error.

Unlimited breaking capacity

Normal working current flows through the bridge.

The arc pressure produced by the high breaking capacity fuse will close the nonlinear resistor, which will distinguish the arc of the fuse.

Once equipped with a nonlinear resistor to absorbs the magnetic field, the breaking capacity may be substantially enlarged.

The system will never experience an anticipated impact current.

   The failure current is broken within1 ms and drops to 0 subsequently.The breaking current value l p will be onlyabout one tenth of the peak short circuit value l max.

   The system will experience a much smaller electric force,with the passed l²t being only one several thousandth of that in a breaker-type protector.

No damaging overvoltage in the process of disconnection

   The zinc oxide nonlinear resistor will limit the over voltage within the 2.5-time rated phase voltage specified by the national standard. 

Advantages of high-capacity fast switching devices used in electric systems

Much lower investment

   The mechanical strength design of the electric equipment may be slackened as the equipment with this device will not be impacted by any strong short circuit current.

   The size of the conductor may be reduced due to the electric equipment's fast disconnection and lower breaking current that eliminate the problem of thermal instability.

 Protection for large electric generators against outlet short circuit 

   With a large breaking capacity,it is an ideal breaking device for electric generator outlets and

substations.

   Electric generators and transformers areprotected fast and effectively.

Much lower investment requirement for system expansions and network operations 

 At a short circuit, HDF quickly Disconnects a system with the load-side breaker handling a short

circuit current of  a single transformer. It will not be necessary to replace the Original switching equipment for system expansions. Electric systems' reliability will be raised With reduced voltage drops at heavy load starting.Operations will be more economical.

Parallel connection of HDF and reactor as the most economical and efficient limiting scheme 

   Normally, HDF short connects the reactor to avoid huge power consumption by the reactor and the voltage drop at the starting of a large motor.At a short circuit, HDFdisconnects quicklyand the load-side breaker's breaking current is limited by the reactor within allowable levels.

In the design of a new power supply system, the impedance of the reactor may be raised to help

further reduce the load-side breaker's breaking current,thereby reducing the cost.   

Higher quality of power supply for important loads that do not allow any instant outage or that require forced auto-starting 

At a short circuit, HDF disconnects quickly and activates the reactor.The residual voltage on the reactor may be designed to a level that is sufficientTo maintain the operation of an important load.

Model specifications and technical parameters

Technical parameters

Construction of high-capacity fast switching device

        Non-cabinet construction 

Cabinet-type construction 

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Operational Environment

Ambient temperature:  -40ºC ~ 50ºC

Altitude: not more than 1,000 meters; special design neededforaltitude of over 1,000 m.

Environmental conditions: free from dust, corrosive gas, steam, or explosive gas

Installation: indoors

Relative humidity: 90%

Packaging, transportation and storage 

To be packed in wooden case, with the cabinet base fastened to the bottom panel of the package.

Not to be transported over long distance on highways below grade three.

May be repacked for shipping as necessary.

To be stored in a dry warehouse with good ventilation if not used for a long time. Not to be stored outdoors for long. Main components of HDF shall be free from collision, dampness or exposure to the sun when in transportation.

Selection of parameters and technical service

Our HDF design shall accommodate parameters of customer's generator, transformer and line arrangements.

Cabinet design shall be made according to the size of the customer's installation site.

Assistance and technical guidance may be provided on request for on-site installation and testing.

The bridge's disconnecting signal must not be open circuited. It should be safely shorted for installation and testing.

Instructions for ordering

Customers shall provide parameters/drawings of their generator, transformer and site line arrangements. 

Customers shall indicate types, specifications and quantity of spare parts they need.