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Megger GPS Timing Reference

MGTR-II

 
  • MGTR-II
  • Overview  
  • Application  
  • Downloads  
Overview
  • Small and lightweight
  • Easy to use programmable output pulse for synchronized end-to-end testing
  • 100 ns accuracy within minutes of startup, 12-channel GPS timing receiver
  • Near-Rubidium stability during temporary GPS signal loss
  • IRIG-B serial time code output
  • Standard one pulse-per-second (PPS) output
  • Event time tag (ETT) time stamp with 100 ns resolution

The MGTR-II is a small, lightweight, field portable, GPS satellite receiver system specifically designed to perform end-to-end tests of line protection schemes, with Megger SMRT, MPRT and PULSAR relay test systems. The MGTR-II provides a precise programmed output pulse (POP), with 100 nanoseconds of resolution. This output pulse provides a trigger synchronization of two or more SMRT, MPRT or Pulsar test systems to less than ±1 µ Sec of the Universal Time Coordinated (UTC).

The MGTR-II consists of a twelve-channel GPS timing receiver integrated with proprietary microprocessor-controlled timing and interface logic. The MGTR-II simultaneously tracks all available GPS satellites. The microprocessor-controlled timing and interface logic derives precise timing information. In addition, the MGTR-II provides a standard 1 Pulse Per Second (PPS), and ASCII serial time message, external event time-tag, an IRIG-B serial time code output signal and most importantly, a programmable output pulse for performing end-to-end tests.

The unit comes with a 50 foot (15.2 m) long cable and all-weather, high-performance, high noise immunity antenna with an integrated low-noise preamplifier. The antenna comes with a 4 inch tall antenna mount.

Control of the MGTR-II is through a standard RS-232 serial connection. Software is provided to communicate to, and control the MGTR-II unit.

Application

Once energized, and after a period of time tracking GPS satellites, the accuracy of this unit approaches the accuracy of the Cesium clocks in the GPS satellites. This insures the highest accuracy possible for triggering end-to-end tests, as well as other timing applications. In addition to the Programmable Output Pulse for performing end-to-end tests, the 10 MHz output is extremely high quality in terms of phase noise and spectral purity.

Two of the most advanced characteristics of the MGTR unit are the Intelligent Holdover™ and FastStart™ features. The Intelligent Holdover feature provides near-Rubidium holdover characteristics in the absence of GPS signals. This can be especially useful when performing end-to-end tests near government facilities, which may locally block GPS signals from time to time. This allows high accuracy triggering even when not receiving GPS timing signals. Under normal operating conditions, the FastStart feature brings the MGTR unit to high precision timing and stability within just minutes of applying power.

Typical test equipment set up for end-to-end tests is shown in the following figure. The test system shown consists of an MPRT relay test set, an MGTR satellite receiver and a personal computer to control the MPRT and MGTR units. A typical notebook computer will have a variety of communication ports. Shown in this figure the RS-232 port is being used to control the Programmable Output Pulse of the MGTR satellite receiver. A PCMCIA IEEE-488 card is being used to communicate to the MPRT test set, and a USB to RS-232 Serial interface is being used to communicate with the relay system under test.

The three phase voltage and current outputs from the MPRT are connected to the relay under test. The breaker sensing inputs of the relay are connected to the binary output terminals of the MPRT, which will serve to simulate the circuit breaker. The relay trip contacts are connected to the binary input terminals of the MPRT. The MGTR units at the opposing terminals, with programmable trigger outputs, are programmed to trigger the MPRT test sets less than 1 microsecond of the UTC. This provides the synchronized outputs of multiple relay test sets at terminals that can be a hundred miles apart. Connections to SMRT are similar to those shown below.

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