April 27, 2009

How to Use Coordinaide™ to Specify IntelliRupter^® PulseCloser TCC Curves — Part 3: Initial Trip/Test Operations and Trip Elements

Part III of a Series.

This is the third in a series of articles describing how Coordinaide — The S&C Protection and Coordination Assistant can be used to specify time-current characteristic (TCC) curves for S&C IntelliRupter PulseCloser. Protection profiles and overcurrent directionality were discussed in last month’s article. This installment discusses the selection of Initial Trip/Test Operations and the Trip Element. Future articles will explain how to specify and save individual TCC curves, view and edit saved TCC curves, and load TCC curves into the IntelliRupter control.

Initial Trip / Test Operation

When a fault is detected on the feeder by a phase, ground, or negative-sequence element, the relayed circuit breaker or recloser will trip and interrupt the fault. The circuit breaker will remain open until the fault damage, if any, is repaired; it can then be manually closed to re-energize the circuit. A recloser, on the other hand, will automatically close and open up to four times . . . until either the circuit remains energized (i.e., the fault was temporary) or the recloser locks open after the fourth attempt (i.e., the fault was permanent).

For IntelliRupter, the first trip operation is referred to as the “Initial Trip.” Subsequent trip operations (similar to a recloser going through its operating sequence) are referred to as test operations. IntelliRupter can have up to four test operations (“Test 1,” “Test 2,” “Test 3,” and “Test 4”). IntelliRupter also has two additional types of trip operations, “Initial Trip IFS” (Intelligent Fuse Saving) and “Sequence Coordination.”

How to Select the Initial Trip/Test Operation in Coordinaide

“Initial Trip” and “Test 1” through “Test 4” are selected from the “General” section of the “TCC Page” for IntelliRupter. There are seven types of trip operations in total, described as follows. See Figure 1.

• Initial Trip. This refers to the first time IntelliRupter opens in response to a fault.
• Initial Trip IFS (Intelligent Fuse Saving). This also refers to the first time IntelliRupter opens in response to a fault. But the TCC curve selected is specifically designed to coordinate with a particular downstream fuse. In conventional fuse saving schemes, the upstream protective device is selected to operate fast enough to “save” the downstream fuse, which would otherwise operate to clear the fault. Intelligent Fuse Saving configures IntelliRupter such that if the fault current is above the point at which the fuse would operate faster than IntelliRupter, IntelliRupter operates on a delayed curve . . . so only the fuse operates to clear the fault. The benefit? Customers downstream of IntelliRupter do not experience a momentary outage.
• Test 1 through Test 4. This refers to the second and subsequent times IntelliRupter opens in response to a fault.
• Sequence Coordination. The Sequence Coordination Elements maintain proper coordination between IntelliRupter and a downstream IntelliRupter or recloser. If the fault is cleared by a downstream device, IntelliRupter will shift to a slower TCC curve to allow the downstream device to complete its full test sequence, thereby preventing miscoordination between the two devices.

Figure 1. Selection of IntelliRupter’s Initial Trip/Test Operation in Coordinaide.

The following rules apply to selection of IFS TCC curves:

1. An Initial Trip TCC curve (phase or ground) must be selected if you wish to select an Initial Trip IFS TCC curve (phase or ground).
2. Initial Trip IFS and Sequence Coordination operation are mutually exclusive. You can have one or the other, or neither, but not both.
3. IFS phase and ground settings must be the same.

How to Select the Trip Element in Coordinaide

Once the Initial Trip / Test Operation has been selected, the next task is to select the Trip Element. It’s also selected from the “General” section of the “TCC Page” for IntelliRupter. IntelliRupter has several available trip elements, including Phase, Ground, Negative Sequence, and Sensitive Earth Fault. See Figure 2.

Figure 2. Selection of IntelliRupter’s Trip Element in Coordinaide.

Putting It All Together

Although it is unlikely that a TCC curve will be specified for every trip operation and for all trip elements, it’s nonetheless possible to specify up to 25 unique TCC curves for IntelliRupter, for a given protection profile and direction. Refer to Table 1.

Table 1. Initial Trip / Test Operations Available for IntelliRupter

Initial Trip — Base Curves	Phase Ground Negative Sequence Sensitive Earth Fault
IFS	IFS Phase IFS Ground
Sequence Coordination	Phase Ground Negative Sequence
Test 1	Phase Ground Negative Sequence Sensitive Earth Fault
Test 2	Phase Ground Negative Sequence Sensitive Earth Fault
Test 3	Phase Ground Negative Sequence Sensitive Earth Fault
Test 4	Phase Ground Negative Sequence Sensitive Earth Fault

Launching Coordinaide

If you’d like to practice specifying IntelliRupter TCC curves, you’ll need to launch Coordinaide. Simply click on the Coordinaide link that appears in the “Support” section of the home page. Additional links appear on applicable product pages (e.g., Type XS Fuse Cutouts, Positrol® Fuse Links, etc.). These links are on the left-hand side of the page in the “Helpful Links” section, immediately above the “TCC Curves” link.

Next month’s article will describe how to specify and save individual IntelliRupter TCC curves.

View Part 1 of this article.

View Part 2 of this article.