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VAMP 221/321: What is the difference between using an optical point sensor and a fiber loop sensor?

Issue
The advantages and disadvantages of using an optical point sensor and a fiber loop sensor for arc flash protection.

Product Line
VAMP 221/321 Protection Relays

Environment
Arc Flash Protection Relays

Cause
Optimization of an arc flash protection solution by specifying either optical point or fiber loop sensors.

Resolution


                                                                          Figure 1

                                                                           Figure 2

Fiber loop sensor technology offers the following advantages when compared to the point sensor:
  1. Significantly reduces the cost of installation. A single optical fiber sensor can be as long as 200 feet, typically covering the same protection zone associated with conventional bus-differential protection but at a much lower cost than point sensors as shown in Figure 2.
  2. The loop approach eliminates any concerns about shadows from internal structures that might block the direct exposure to an arc flash.
  3. Optical point sensors are installed in every enclosed compartment and has a wired coverage area as shown in Figure 1.
  4. If the fiber sensor is configured in a loop, it can provide regular self-checking of the sensor’s integrity and continuity, producing an alarm if a problem is detected.

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