MR and MB — Manual Reset
Sales and Ordering Information
Please contact Customer Service at
SEL Lake Zurich, Illinois at +1.847.362.8304
or by email at csrlz@selinc.com
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Manual Reset (MR) Fault Indicators employ a magnetic principle using two magnetic elements. One is the yoke which is demagnetized by the fault current, allowing the other to act on the display and cause a reflective red target to show. The target is held in place magnetically until the MR is reset using the Manual Reset Tool.
The MR is secured to the line by means of overcenter toggle clamps and may be applied or removed by a hot stick. MR Fault Indicators have a response time of 12 ms at the trip rating. The display has a red reflective target area of 3.3 square centimeters.
Manual Button (MB) Reset Fault Indicators use a magnetic field from the fault current to act as an overcenter magnetic toggle to produce fault indication. No mechanical triggers or latches are used. The MB display features a reflective red/white target. A faulted line condition is displayed by the red target while a normal condition is displayed by the white target. The MB is reset by pressing a magnetic button integral to the indicator, thus making removal from the line unnecessary for reset.
Both MR and MB fault indicators have hermetically-sealed ultrasonically welded housings and stainless-steel, vinyl-coated clamping mechanisms that make them suitable for use in harsh, submersed, and corrosive environments.
- After a fault occurs, use an MR or MB before reclosing for inexpensive, efficient fault location.
- Line-powered, battery free.
- The built-in reset button in the MB model eliminates the need for a separate reset tool.
- The MR model is available in a convenient kit to keep on a truck— three MRs and a reset tool in a sturdy, lightweight carrying case.
- MR models are also applicable on overhead systems. MB models are only for underground applications.
- More than 50 years of field-proven reliability.
| Nominal Trip Ratings |
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| MB |
25 to 800 A |
| MR |
100 to 800 A |
| Trip Tolerance |
±10% |
| System Voltage Range |
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| Overhead (MR only) |
Up to 38 kVL-L |
| Underground |
Matches the URD cable rating |
| Maximum Fault Current |
25 kA for 10 cycles |
| Trip Response Time |
8 ms |
| Outer Diameter Clamping Range |
0.25" to 1.4" (please specify the clamping diameter or range when ordering) |
| Temperature Range |
—40° to +85°C |
| Approximate Weight |
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| MB |
170 g (0.37 lbs) |
| MR |
140 g (0.31 lbs) |
Installation Instructions