IS220PRTDH1B - RTD Input Pack

Functional Description

IS220PRTDH1B is a RTD Input Pack manufactured and designed by General Electric as part of Mark VIe series distributed control system. The Resistance Temperature Device (RTD) Input (PRTD) pack interfaces one or two I/O Ethernet networks with an RTD input terminal board. The pack includes a processor board that is shared by all Mark VIe distributed I/O packs as well as an acquisition board dedicated to the thermocouple input function.

IS220PRTDH1B Functional Description
The PRTD pack only supports the simplex operation. The pack is powered by three-pin power input and a DC-37 pin connector that connects directly to the associated terminal board connector. Dual RJ45 Ethernet connectors are used for output. LED indicator lights provide visual diagnostics. The I/O pack can handle up to eight RTD inputs and the TRTD terminal boards can handle up to 16 RTD inputs.

IS220PRTDH1B Processor Features

• The processor board is linked to an acquisition board dedicated to the function of the I/O pack or module. When input power is applied, the soft-start circuit increases the voltage available on the processor board.
• The local power supplies are turned on in sequence, and the processor reset is disabled. After finishing self-test routines, the processor loads application code specific to the I/O pack or module type from flash memory. The application code reads board ID information to ensure that the application code, acquisition board, and terminal board are all correctly matched.
• When there is a good match, the processor attempts to establish Ethernet communications, beginning with a network address request. The address request makes use of the industry-standard dynamic host configuration protocol (DHCP) and the terminal board's unique identification.
• Following Ethernet initialization, the processor programs the on-board logic, runs the application, and allows the acquisition board to begin operation. The processor application code contains all of the logic required for the I/O pack to operate from one or two Ethernet inputs. When two Ethernet inputs are used, both network paths are always active.
  A failure of either network will not affect the operation of the I/O pack or module, and the failure will be indicated by the working network connection. This configuration is more fault-tolerant than a traditional hot-backup system, which uses the second port only when the primary port fails.
• The Ethernet ports on the processor auto-negotiate between 10 MB/s and 100 MB/s speeds, as well as between half-duplex and full-duplex operation.

Auto-Reconfiguration

• The Auto-Reconfiguration feature allows the operator to replace I/O packs without having to manually reconfigure each pack or module. When the controller detects an I/O pack booting with a different configuration and the Auto-Reconfiguration feature is enabled, a reconfiguration file is automatically downloaded from the controller to the I/O pack.
• The bootload, baseload, firmware, and parameters are all reconfigured. Unless it already has the latest version, each I/O pack is updated with the current configuration that matches the configuration used by the controller.

Analog Input Hardware
The RTD terminal board provides eight three-wire RTD inputs to the PRTD input board. Each RTD, which can be grounded or ungrounded, receives a 10 mA dc multiplexed (not continuous) excitation current from the pack. With a maximum two-way cable resistance of 15, the eight RTDs can be located up to 300 meters (984 feet) from the turbine I/O cabinet. The pack's A/D converter samples each signal and excitation current four times per second in normal mode and 25 times per second in fast mode, with a time sample interval related to the power system frequency.

Compatibility

The number of I/O packs used in a signal path is referred to as the control mode:

• Simplex employs a single I/O pack and one or two network connections.
• Dual employs two I/O packs with one or two network interfaces.
• TMR employs three I/O packs, each with one network connection.

The galvanic isolation of the TRD input circuit is provided by the PRTD. This necessitates changes to the terminal board transient protection, which is available on the TRTDH1D and TRTDH2D boards. The H1D version of the board includes filtering that is compatible with the PRTD's standard scan rate. When the fast scan rate of the PRTD is selected, the H2D version of the terminal board provides less filtering to allow proper performance. The incompatibility will be reported if the PRTD is mounted on an earlier revision of the TRTD board, but no physical damage will occur.