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Collaboration solutions for the primary flow transformers with the recloser load
Collaboration solutions for the primary flow transformers with the recloser load

We will use the method of coordination "is of balance" (conservative), in ignoring the effects cooling flow requirements during closed recloser repeat (the next point open).

Coordinate resources for the flow / load the recloser

The recloser detects, cut power lines too, and then close automatically repeated to close the power supply route. Most of the incident distribution system on line (probably 75 to 80%) pertaining to temporary and lasted only a few cycles to several seconds.

With the ability to "close cooperation and repeat" of the recloser, can eliminate power cuts lasting supply system due to this problem temporarily. However, if the problem is not permanent but temporary, recloser will "lock circuit" closed after a number of repeated unsuccessful (usually three or four times), and thereby providing lo isolate of incidents from the system.

Cutting close automatically repeat (recloser) has the ability to set the time to coordinate with other protective devices and limit the area affected by the problem permanent. Often tasks disarmament problems first (sometimes two operations disarmament problems first) is made by characteristic timing "fast", so a temporary solution unless the problem temporarily before devices protect the load impact. The operation was then done with pre-defined time delay to allow protective devices near the cut line than trying to eternal problems, thereby limiting the scope of continuous power supply.

The layout is much the scheme is called "saving for running" because only reacts to demand flow problems within its permanent protection.

The application mentioned in this article, the primary flow for transformers located at the source of the recloser. Objectives are not for running off before recloser impact "key circuit" in response to the eternal problem. Current value of the biggest problems that demand flows and recloser will coordinate is usually worth less than the following values:

    * Ability to cut most of the recloser or for running, or
    * Communication point of lowest flow curve of the flow curve for impact equivalent biggest recloser (ie curve "key circuit").

By the method of coordination "is of balance", ignoring the cooling flow requirements during repeat play (the next point open). You only need to sum up the thermal effects, ie heat input of each impact of the recloser. Thus, the key circuit curve was constructed by taking the sum of the total time minus the number of relevant tasks fast and slow, at different flow rates, the following formula:


TI is a key point on the curve equal to the largest circuit (maximum equivalent lockout curve) of the recloser, at selected current (I).

P is the amount of shortening of the running for the flow with initial loading (preloading), represented by the decimal fraction of the total flow of time for running.

Trj the time except at the largest current I for the second impact on j (the point to close) of the recloser.

n is the number of impact (the next point play) of the recloser.

Because the bridge flows must allow key circuit recloser impact that should not be built off curve key equivalent circuit recloser's largest. Fast curves (A) of the recloser is generally announced to the largest test score. However, the slow curve (B, C and D) Left published a test for nominal and therefore must be edited (the maximum value) of a positive tolerance, but the assumption is 10 %.


Consider the case in medium voltage transformer stations in rural areas only a transformer, protected for running, with three (or less) to provide recloser road. List of parameters for the primary flow, transformers, and the recloser load is as follows:

Transformers. Three-phase transformers, power facilities (OA - cooled air natural convection) is 7500 kVA, voltage of 115 kV primary, secondary voltage is 13.2 kV. Capacity when cooled forced air (FA) is 9375 kVA (125%). Electrical short circuit resistance of the transformers is 7.5%. Three-phase current biggest problem the secondary is 478 A (2,000 MVA), as seen from the primary transformers. Auction of the line transformers are delta / star earthing.

Demand flows. Running the primary demand is for 65 A flows, the standard speed, voltage 115 kV, SMD-2B type of company S & C. Full load current of transformers, as of the forced cooling mode is 47 A. At this load of transformers, the load demand flows are subject to 72% (47/65 = 0.72). Coefficient with preloaded (preload adjustment factor), defined by S & C Data Bulletin 210-195 is 0.88.

Recloser the road provides. Recloser the Cooper recloser type load is controlled by hydraulic W, nominal voltage is 14.4 kV, nominal current is 560 consecutive A. Line harp impact phase is 280 A (coil 140 A), the order effect is a rapid effect (A) and three slow effect (C). Closed loop time gap between fast impact and impact delay first 0.5 s (real time). Between the impact on delay, the gap closed loop time is 5 s.

Exercises on coordination, using software Coordinaide

To do exercises to coordinate, execute programs Coordinaide by clicking on the link (link) on the S & C website you are viewing. The home page link Coordinaide. Can find additional links in the drop-down menu from the label (label) "Support" as well as in the applicable product page, for example, runs S & C Bridge SMD type. Links-style tab is located on the left page, right under the "For more Information" tab and on the "light for product (characteristic time-current product).

Selected for the primary flow, transformers, and the recloser load, according to the instructions below.

Step 1. Enter general information

Project: Exercises in combination for flow / recloser

Date: [Do Coordinaide offer]

By: Option

Step 2. Enter information about the system and select equipment

Three-phase voltage, kV: 115

Short circuit current expectations, Ampe name matching: 10,000

Equipment 1: Bridge flow

Equipment 2: Transformer (curve damage)

Equipment 3: Recloser

Click "Continue" after entering information and selecting equipment. You will return to the "devices" first.

Step 3. Select and device parameter

Equipment 1. Bridge flows the primary transformers (Select the parameters)

Manufacturers: S & C

Model: SMD-2B

Speed: Standard

Voltage range, kV: 115-138

Nominal current, A: 65

After selecting the parameters of the device 1, click "Continue". Screen will display line features the time-current of the device 1.

Equipment 2. Transformers (Select the parameters)

Primary three-phase voltage, kV: 115 [by providing Coordinaide]

Secondary three-phase voltage, kV: 13.2

Capacity 3 phase, kVA: 7500

Short circuit impedance,%: 7.5

Current problems, A name matching: 10,000 [provided by Coordinaide]

Show the points for goods? _Co _Khong (Default)

The Auction Line: Triangle / Star Grounding

After selecting the parameters of the device 2, click "Continue". Screen will display line features the time-current of the device 2.

Equipment 3. Recloser Route power supply (Select the parameters)

Coordinate with: _Hoist been the source of the load _Electric. See Note 1

Method of coordination: _He number of outstanding cooling _Co (default). See Note 2

Manufacturers: Cooper (Mc Graw): Hydraulics

Type: W

Voltage range, kV: 14.4 [provided by Coordinaide]

Order effects cutting phase: 1 Fast / Slow 3

Fast curve "A"

Slow curve "C"

Nominal current of the coil, A: 140

Order effects cut Grounding: Skip within this example

Note 1: Recloser placed in the load flow of the primary requirements, so select "Coordinate with the source device (the default in this example)

Note 2: Select "method of balance is" to ignore the effects cooling flow for the primary period between the last repeat recloser closed (continued commencing). Ban is so repeat this example using the method more accurate, taking into account the cooling system, and then compare the results.

After selecting the parameters of the device 3, click "Continue". Screen will display line features the time-current device 3.

Step 4. On to the "Results"

Click on the tab labeled "Results". You will coordinate system with the loga loga-curve characteristic time-current (time-current characteristic - TCC) of the device you selected.

If you wish, you can change the current scale on the graph, from the default mode is 5 to 100,000 to 0.5 A to 10,000 A. You can also remove the slash on the TCC curve to read the graph clearer. And you can zoom (magnification) of a specific part of the graph by entering values on the current and the current and time on the appropriate box.

If you want to see the TCC curve full size or full summary information, the custom case, you should click on the "Printer Friendly Graph" or "Printer Friendly Summary.

Now, let's review the TCC curve example of cooperation mentioned above.

Device 1, for the primary flow 65 A, the standard speed, the red curve.

Device 2, curve damaged transformers, black curve. Device 3, the recloser load, the orange curve. Two curves is darker than the orange curve Quick (A) and curve Slow (C) of the recloser, based on data by the recloser manufacturer announced. Orange curve is the curve key piece line equivalent recloser's largest, reflecting the tolerance of the ocean.

A demand flow rate of 65 standard very good protection transformers can be seen as the fact that the curve of the bridge complete disarmament flow curve cut damaged transformers in the line under the maximum value obtained from any type of format. Demand flow, according to published or resistant peak load of 107 A, which means that transformers can carry the load in close to 280% of the value indicated on the label machine, far exceeding the nominal value by the cooling mode OA / FA (125% value on the label machine).

Unfortunately for the primary flow does not coordinate well with the curve "key line" equivalent recloser's largest, because time is running most of the current flows for 478 A (0.42 s) small than the current curve key equivalent biggest recloser at this line (0.69 s). Note that the curve of the recloser secondary was shifted to the right by about 15% of the value of electric current, to consider the current imbalance between the primary and the secondary, this could happens when a phase-phase short circuit is not connected to the secondary ground.

When you encounter this situation, the natural reaction is to select for the primary flow is greater than the current level, for flows with characteristic time-current slower, or both ... until they achieve coordination. Although this solution may lead to a full coordination between demand flow and integrity recloser, however, affect the protection of transformers, and the results are not yet optimal. Before selection for a larger flow or flow feature for time-current slower, repeat this exercise using more accurate methods: the method taking into account the cooling system.

You will find that the primary demand flows initially selected as entirely appropriate

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