IS200TRTDH1C - RTD Input Terminal Board

Functional Description

IS200TRTDH1C is an RTD Input Terminal Board manufactured and designed by General Electric as part of the Mark VIe series used in GE distributed gas turbine control systems. There are 16 three-wire RTD inputs on the RTD Input (TRTD) terminal board. Two barrier-type terminal blocks are connected to these inputs by wiring. To guard against surges and high-frequency noise, the inputs feature noise-reduction circuitry. TRTD interacts with one or more I/O processors to transform inputs into digital temperature values and send those data to the controller.

There are four different TRTD versions, as follows:

• The TRTDH1B is a TMR variant that uses six DC-type connectors to fan out the signals to three VRTD boards.
• A simplex board called TRTDH1C has two DC-type connectors for VRTD.
• The TRTDH1D is a simplex board with two PRTD, normal scan DC-type connections.
• The TRTDH2D is a simplex board with two PRTD, quick-scan DC-type connectors.

Installation

The 16 RTDs' wires should be connected straight to the two terminal blocks on the terminal board. With 24 terminals that can accommodate wires up to #12 AWG, each block is secured in place with two screws. On the left-hand side of each terminal block, a shield terminal strip connected to the chassis ground is present.

The TRTDH1B board in a TMR Mark VI control system provides redundant RTD inputs by fanning the inputs to three VRTD boards in the R, S, and T racks. The inputs comply with the same environmental, resolution, suppression, and function standards and regulations as the TRTDH1C terminal board; the quick scan, however, is not accessible.

Operation

For each RTD, which can be grounded or ungrounded, TRTD provides a 10 mA dc multiplexed (not continuous) excitation current. The 16 RTDs can be placed as far away from the turbine control cabinet as 300 m (984 ft), with a maximum two-way cable resistance of 15 ohms. When scanning in normal mode or quickly, the I/O processor's A/D converter samples each signal and the excitation current 25 times per second and four times per second, respectively. The time sample interval is based on the power system frequency. For the chosen 15 RTD kinds, the software does the linearization.

Out-of-range measurements can identify RTD short and open circuits. To avoid negative effects on other input channels, an RTD that is found to be outside the hardware limits is deleted from the scanned inputs. In 20 seconds, repaired channels are automatically restored; alternatively, they can be manually restored.

High-frequency decoupling to the ground is present at the signal entrance for all RTD signals. In order to prevent any RTD signals in the control database from being lost due to the failure of a single cable or I/O processor, RTD multiplexing in the I/O processor is managed by redundant pacemakers.