SCADA 2000 Series Input/Output
2000 Series I/O: MSE-Tetragenics designed the 2000 Series I/O System for use in the harsh electrical environments prevalent in electrical generating plants, substations, and switchyards.
All cards are double-height Eurocards of the following dimensions: 9.2" High x 6.3" Deep x .8" Maximum Thickness.
A typical 2000 Series I/O card has two connectors on the back. The lower half of the card (port 2) has a 96-pin connector which interfaces to the 2000 Series bus. The top half of the card has a connector (port 1) which interfaces to the external I/O. The front of each card has a metal panel which is secured to the chassis using machine screws.
Easy Maintenance/Replacement
A very important aspect of this design is that you can remove the I/O cards without changing any field wiring or plant-side I/O connections. The benefit is that the wiring bundle or cable does not have to be moved, folded, or flexed to change I/O cards.
The input and output characteristics are critical to the proper operation, installation, reliability, and maintenance ease of the system. The I/O subsystem provides the protective buffer between the harsh electrical environment of the plant and the "electrically sterile" environment of digital computers.
ANSI/IEEE Standards
ANSI/IEEE Surge Standard C37.90 defines the ANSI/IEEE Surge Withstand Capability. Both the transverse and common mode Surge Withstand Capability tests defined in C37.90 have been applied to representative I/O points of each type provided, using either the boards supplied or boards of identical design. Sufficient testing has taken place to indicate that these tests can be applied to each field wiring point without damaging any component so that it must be replaced or recalibrated to function properly after the Surge Withstand Capability waveform has been removed.
TopTemperature Specifications
The operating temperature range limits for the 2000 Series family of boards are 0 to 60 degrees C. The storage temperature for the 2000 Series family of boards is -40 to 70 degrees C. The humidity specifications for the 2000 Series family of boards are 95% noncondensing.
TopAnalog Inputs (AI)
The Tetragenics 2000 Series System offers flexibility because it supports the following analog input signals:
| ±10 Vdc, | ±1 mA, | 0 to 10 Vdc, |
| 0 to 5 Vdc, | 4 to 20 mA, | 10 to 50 mA, |
| 0 to 200 mV, | ±1 Vdc, | ±5 Vdc. |
The analog-to-digital subsystem is optically isolated from the computer logic of the RTU or Controller, with at least 1.5 kV of isolation. Burden resistors are an integral part of the analog input termination.
Differential analog inputs are fed into the 2000 Series RTUs via the 16 Differential Analog Input Multiplexor Board. The differential input signals are terminated on the 16 Differential Analog Input Termination Panel. A shield termination is provided that is connected to ground within the RTU.
TopDigital Inputs: Sequence of Events and Status DI
Digital inputs are optically isolated, with at least 3.0 kV of isolation. For optimum noise immunity, the detected transition level for 125 Vdc inputs should be in the range of 90 to 100 Vdc, for 48 Vdc inputs, the transition point should be approximately 29 volts, and for 24 Vdc inputs, the transition point should be approximately 19.5 volts. For Transistor Transistor Logic or 12 V inputs, standard logic transition levels apply. Interface hardware is available for either dry contact or voltage keyed inputs. When dry contact inputs are used, the interface hardware supplies the voltage (usually from the station battery) to provide proper indication. For the voltage keyed option, the station battery voltage is fed to the interface by the external equipment. Each digital input circuit is similar to a polarized relay coil.
Other input options available are ±5 Vdc, 10 Vdc, and Transistor Transistor Logic. All options require 5 mA (max) current.
The 2000 Series 32 Digital Input Board has a debounce filter as small as 2 milliseconds. Individual termination of field wires for signal high and signal low is provided for each discrete input point.
TopBinary Coded Decimal, Binary, and Gray Code Inputs
To Standard digital input boards are used for Binary Coded Decimal, Gray Code, or Binary input. The software polls the appropriate inputs for their states and converts the inputs to the corresponding engineering value. Sixteen DI points are used to represent four Binary Coded Decimal digits or one binary or gray code value. Each DI point sinks 5 mA. Input options include Transistor Transistor Logic (0-5 Vdc), ±5 Vdc, 12 Vdc, 24 Vdc, 48 Vdc, and 125 Vdc.
If external inputs are dry contacts, excitation is provided through a pull-up resistor to the appropriate isolated voltage source. If a strobed input is needed, the strobe is connected to a single DI in a bank jumpered for interrupt. Individual termination of field wires for signal high and signal low is provided for each discrete input point.
TopHigh-Speed Counter Inputs
High-speed counter inputs provide accumulation of high speed pulses (up to 20 kHz). The input includes hardware which provides a true debounce of a C-type contact input. Also, the hardware provides a 16-bit counter register. Each counter input can be jumpered to operate in two different modes: (1) the counter mode and (2) the frequency mode. In the counter mode the counter registers increments when the C-type contact input goes to the non-normal state. The counter register rolls over to zero when it reaches a count of 65,535.
In the frequency mode, the hardware counts the number of full-cycle transitions that have occurred in a given time period (jumper selectable for 2 seconds, 1 second, .5 seconds, or .25 seconds). Input options include 24 Vdc, 48 Vdc, and 125 Vdc. Individual termination of field wires for the normal open, normal closed, and common is provided for each discrete input point.
TopPulse Counter Inputs
Pulse counter inputs include hardware debounce, selection of counting changes regardless of direction or on full cycle, count rate exceeding 10 counts per second, and freeze command capabilities. At initialization time, freezes can be set up to either count continuously and handle rollover, or to clear the counter. Data is not lost in either case. The count is stored in a 16-bit location (65,535 counts). Pulses at least 20 ms long are detected in the "full-cycle" mode. Input options include Transistor Transistor Logic (0-5 Vdc), ±5 Vdc, 12 Vdc, 24 Vdc, 48 Vdc, and 125 Vdc. Individual termination of field wires for signal high and signal low is provided for each discrete input point.
TopPulse Duration Inputs
Pulse duration inputs are software realized using Tetragenics digital input cards. When a state transition occurs, the time (to the nearest millisecond) is read and saved. When the next state transition occurs, the time is read again. The first time is subtracted from the second time and the resulting time difference is converted to engineering units. We have ±1 millisecond time resolution on the time the transition is detected. Individual termination of field wires for signal high and signal low is provided for each discrete input point.
TopDigital Outputs (DO)
Digital outputs are interposing relays or solid-state current drivers, for the 2000 Series RTU's relay socket panels, that accommodate compliant relays. Both latching and momentary relays are available.
When a control point is activated, its point remains active for "n" ms if no feedback occurs. However, if the appropriate change is detected, then the point remains active for "m" ms after the change is detected. The constants "n" and "m" can be set for each DO via the database.
TopAnalog Outputs (AO)
The MSE-Tetragenics system supports the following analog output signals: ±10 Vdc, ±1 mA, and 0-20 mA. The analog outputs have a resolution of 12 bits. Shown below is the available output ranges and their corresponding accuracies:
- ± 10 V, ± 5 V, 0-10 V: ± .025% of Full-Scale Range
4-20 mA: ± .075% of Full-Scale Range
The current output can be powered externally with a 24 Vdc power supply and drive loads between 0 and 500 Ohm. The voltage outputs have an output impedance of less than 10 Ohms.
TopTermination and Packaging
19" Rack Mount (Panel Termination)
The termination of field wiring and packaging are critical considerations that impact the ease of installation, the ease of testing, and the ease of repair and reliability. All 2000 Series field I/O wiring terminates on screw terminals that can accept wire as large as #12 AWG and as small as #22 AWG. Ample space is allowed for field wiring bundles, including room to neatly "dress-out" field wiring to terminal strips in the same plane as the terminal strips, since it is not acceptable to have the wiring bundle in the plane perpendicular to the terminal strips which obscures the terminal screw. Support is provided to adequately secure or tie down field wiring bundles within the cabinet.
All field wiring connections to I/O printed circuit boards are on the rear of the I/O card so that the printed circuit board can be removed or inserted without disturbing field wiring connections or flexing field wires, cables, or bundles.
All chassis, front panels, and termination panels are grounded to provide Radio-Frequency Interface (RFI) shielding.
A screw termination point is provided for each discrete digital input and digital output field wire. In addition, analog input and analog output provide a shield termination terminal.
Double-Height Eurocard Termination
For RTU installations where space is critical, Tetragenics offers a card termination board. One card can terminate up to 16 digital outputs or inputs or 8 single-ended analog inputs, analog outputs, or differential analog inputs.
The board will allow termination of up to 14 gauge wire. Like all Tetragenics termination, you can remove or replace the I/O cards without upsetting field wiring.
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