GESPEEDTRONIC™ Mark VI Turbine Control System

Introduction

The SPEEDTRONIC™ Mark VI turbine control

is the current state-of-the-art control for GE turbines that have a heritage of more than 30 years

of successful operation. It is designed as a complete integrated control, protection, and monitoring system for generator and mechanical

drive applications of gas and steam turbines. It is

also an ideal platform for integrating all power

island and balance-of-plant controls. Hardware

and software are designed with close coordination between GE’s turbine design engineering

and controls engineering to insure that your control system provides the optimum turbine performance and you receive a true “system” solution. With Mark VI, you receive the benefits of

GE’s unmatched experience with an advanced

turbine control platform. (See Figure 1.)

Architecture

The heart of the control system is the Control

Module, which is available in either a 13- or 21-

slot standard VME card rack. Inputs are

received by the Control Module through termination boards with either barrier or box-type

terminal blocks and passive signal conditioning.

Each I/O card contains a TMS320C32 DSP

processor to digitally filter the data before conversion to 32 bit IEEE-854 floating point format.

The data is then placed in dual port memory

that is accessible by the on-board C32 DSP on

one side and the VME bus on the other.

In addition to the I/O cards, the Control

Module contains an “internal” communication

card, a main processor card, and sometimes a

flash disk card. Each card takes one slot except

for the main processor that takes two slots.

Cards are manufactured with surface-mounted

technology and conformal coated per IPC-CC830.

I/O data is transmitted on the VME backplane

between the I/O cards and the VCMI card

located in slot 1. The VCMI is used for “internal” communications between:

■ I/O cards that are contained within its

card rack

■ I/O cards that may be contained in

expansion I/O racks called Interface

Modules

■ I/O in backup <P> Protection

Modules

■ I/O in other Control Modules used in

triple redundant control

configurations

■ The main processor card

The main processor card executes the bulk of

the application software at 10, 20, or 40 ms

depending on the requirements of the application. Since most applications require that speSPEEDTRONIC™ Mark VI Turbine Control System

GE Power Systems ■ GER-4193A ■ (10/00) 1

Figure 1. Benefits of Speedtronic™ Mark VI

• Over 30 years experience

• Complete control, protection, and

monitoring

• Can be used in variety of applications

• Designed by GE turbine and controls

engineering

ific parts of the control run at faster rates (i.e.

servo loops, pyrometers, etc.), the distributed

processor system between the main processor

and the dedicated I/O processors is very important for optimum system performance. A QNX

operating system is used for real-time applications with multi-tasking, priority-driven preemptive scheduling, and fast-context switching.

Communication of data between the Control

Module and other modules within the Mark VI

control system is performed on IONet. The

VCMI card in the Control Module is the IONet

bus master communicating on an Ethernet

10Base2 network to slave stations. A unique poling type protocol (Asynchronous Drives

Language) is used to make the IONet more

deterministic than traditional Ethernet LANs.

An optional Genius Bus™ interface can be provided on the main processor card in Mark VI

Simplex controls for communication with the

GE Fanuc family of remote I/O blocks. These

blocks can be selected with the same software

configuration tools that select Mark VI I/O

cards, and the data is resident in the same database.

The Control Module is used for control, protection, and monitoring functions, but some

applications require backup protection. For

example, backup emergency overspeed protection is always provided for turbines that do not

have a mechanical overspeed bolt, and backup

synch check protection is commonly provided

for generator drives. In these applications, the

IONet is extended to a Backup Protection

Module that is available in Simplex and triple

redundant forms. The triple redundant version

contains three independent sections (power

supply, processor, I/O) that can be replaced

while the turbine is running. IONet is used to

access diagnostic data or for cross-tripping

between the Control Module and the

Protection Module, but it is not required for

tripping.

Triple Redundancy

Mark VI control systems are available in

Simplex and Triple Redundant forms for small

applications and large integrated systems with

control ranging from a single module to many

distributed modules. The name Triple Module

Redundant (TMR) is derived from the basic

architecture with three completely separate and

independent Control Modules, power supplies,

and IONets. Mark VI is the third generation of

triple redundant control systems that were pioneered by GE in 1983. System throughput

enables operation of up to nine, 21-slot VME

racks of I/O cards at 40 ms including voting the

data. Inputs are voted in software in a scheme

called Software Implemented Fault Tolerance

(SIFT). The VCMI card in each Control

Module receives inputs from the Control

Module back-plane and other modules via “its

own” IONet.

Data from the VCMI cards in each of the three

Control Modules is then exchanged and voted

prior to transmitting the data to the main

processor cards for execution of the application

software. Output voting is extended to the turbine with three coil servos for control valves and

2 out of 3 relays for critical outputs such as

hydraulic trip solenoids. Other forms of output

voting are available, including a median select

of 4-20ma outputs for process control and 0-

200ma outputs for positioners.

Sensor interface for TMR controls can be either

single, dual, triple redundant, or combinations

of redundancy levels. The TMR architecture

supports riding through a single point failure in

the electronics and repair of the defective card

or module while the process is running. Adding

sensor redundancy increases the fault tolerance

of the overall “system.” Another TMR feature is

the ability to distinguish between field sensor

faults and internal electronics faults.

Diagnostics continuously monitor the 3 sets of

input electronics and alarms any discrepancies

between them as an internal fault versus a sensor fault. In addition, all three main processors

continue to execute the correct “voted” input

data. (See Figure 2.)

I/O Interface

There are two types of termination boards. One

type has two 24-point, barrier-type terminal

blocks that can be unplugged for field maintenance. These are available for Simplex and

TMR controls. They can accept two 3.0 mm2

(#12AWG) wires with 300 volt insulation.

Another type of termination board used on

Simplex controls is mounted on a DIN rail and

has one, fixed, box-type terminal block. It can

accept one 3.0 mm2 (#12AWG) wire or two 2.0

mm2 (#14AWG) wires with 300 volt insulation.

I/O devices on the equipment can be mounted

up to 300 meters (984 feet) from the termination boards, and the termination boards must

be within 15 m (49.2’) from their corresponding I/O cards. Normally, the termination

boards are mounted in vertical columns in termination cabinets with pre-assigned cable

lengths and routing to minimize exposure to

emi-rfi for noise sensitive signals such as speed

inputs and servo loops.

General Purpose I/O

Discrete I/O. A VCRC card provides 48 digital

inputs and 24 digital outputs. The I/O is divided between 2 Termination Boards for the contact inputs and another 2 for the relay outputs.

(See Table 1.)

Analog I/O. A VAIC card provides 20 analog

inputs and 4 analog outputs. The I/O is divided

between 2 Termination Boards. A VAOC is dedicated to 16 analog outputs and interfaces with

1 barrier-type Termination Board or 2 box-type

Termination Boards. (See Table 2.)

Temperature Monitoring. A VTCC card provides interface to 24 thermocouples, and a

VRTD card provides interface for 16 RTDs. The

input cards interface with 1 barrier-type

reduced by eliminating peripheral instrumentation. The VTUR card is designed to integrate

several of the unique sensor interfaces used in

turbine control systems on a single card. In

some applications, it works in conjunction with

the I/O interface in the Backup Protection

Module described below.

Speed (Pulse Rate) Inputs. Four-speed inputs

from passive magnetic sensors are monitored by

the VTUR card. Another two-speed (pulse rate)

inputs can be monitored by the servo card

VSVO which can interface with either passive or

active speed sensors. Pulse rate inputs on the

VSVO are commonly used for flow-divider feedback in servo loops. The frequency range is 2-

14k Hz with sufficient sensitivity at 2 Hz to

detect zero speed from a 60-toothed wheel. Two

additional passive speed sensors can be monitored by “each” of the three sections of the

Backup Protection Module used for emergency

overspeed protection on turbines that do not

have a mechanical overspeed bolt. IONet is

used to communicate diagnostic and process

data between the Backup Protection Module

and the Control Module(s) including cross-tripping capability; however, both modules will initiate system trips independent of the IONet.

(See Table 4 and Table 5.)

Synchronizing. The synchronizing system consists of automatic synchronizing, manual synchronizing, and backup synch check protection. Two single-phase PT inputs are provided

Application Specific I/O

In addition to general purpose I/O, the Mark

VI has a large variety of cards that are designed

for direct interface to unique sensors and actuators. This reduces or eliminates a substantial

amount of interposing instrumentation in

many applications. As a result, many potential

single-point failures are eliminated in the most

critical area for improved running reliability

and reduced long-term maintenance. Direct

interface to the sensors and actuators also

enables the diagnostics to directly interrogate

the devices on the equipment for maximum

effectiveness. This data is used to analyze device

and system performance. A subtle benefit of

this design is that spare-parts inventories are

on the TTUR Termination Board to monitor

the generator and line busses via the VTUR

card. Turbine speed is matched to the line frequency, and the generator and line voltages are

matched prior to giving a command to close the

breaker via the TTUR. 

An external synch check relay is connected in

series with the internal K25P synch permissive

relay and the K25 auto synch relay via the

TTUR. Feedback of the actual breaker closing

time is provided by a 52G/a contact from the

generator breaker (not an auxiliary relay) to

update the database. An internal K25A synch

check relay is provided on the TTUR; however,

the backup phase / slip calculation for this relay

is performed in the Backup Protection Module

or via an external backup synch check relay.

Manual synchronizing is available from an operator station on the network or from a synchroscope.

Shaft Voltage and Current Monitor. Voltage can

build up across the oil film of bearings until a

discharge occurs. Repeated discharge and arcing can cause a pitted and roughened bearing

surface that will eventually fail through accelerated mechanical wear. The VTUR / TTUR can

continuously monitor the shaft-to- ground voltage and current, and alarm at excessive levels.

Test circuits are provided to check the alarm

functions and the continuity of wiring to the

brush assembly that is mounted between the

turbine and the generator.

F

Flame Detection. The existence of flame either

can be calculated from turbine parameters that

are already being monitored or from a direct

interface to Reuter Stokes or Honeywell-type

flame detectors. These detectors monitor the

flame in the combustion chamber by detecting

UV radiation emitted by the flame. The Reuter

Stokes detectors produce a 4-20ma input. For

Honeywell flame scanners, the Mark VI supplies

the 335Vdc excitation and the VTUR / TRPG

monitors the pulses of current being generated.

This determines if carbon buildup or other

contaminates on the scanner window are causing reduced light detection.

Trip System. On turbines that do not have a

mechanical overspeed bolt, the control can

issue a trip command either from the main

processor card to the VTUR card in the Control

Module(s) or from the Backup Protection

Module. Hydraulic trip solenoids are wired with

the negative side of the 24Vdc/125Vdc circuit

connected to the TRPG, which is driven from

the VTUR in the Control Module(s) and the

positive side connected to the TREG which is

driven from the VPRO in each section of the

Backup Protection Module. A typical system trip

initiated in the Control Module(s) will cause

the analog control to drive the servo valve actuators closed, which stops fuel or steam flow and

de-energizes (or energizes) the hydraulic trip

solenoids from the VTUR and TRPG. If crosstripping is used or an overspeed condition is

detected, then the VTUR/TRPG will trip one

side of the solenoids and the VPTRO/TREG

will trip the other side of the solenoid(s).

Servo Valve Interface. A VSVO card provides 4

servo channels with selectable current drivers,

feedback from LVDTs, LVDRs, or ratio metric

LVDTs, and pulse-rate inputs from flow divider

feedback used on some liquid fuel systems. In

TMR applications, 3 coil servos are commonly

used to extend the voting of analog outs to the

servo coils. Two coil servos can also be used.

One, two, or three LVDT/Rs feedback sensors

can be used per servo channel with a high select,

low select, or median select made in software. At

least 2 LVDT/Rs are recommended for TMR

applications because each sensor requires an AC

excitation source. (See Table 6 and Table 7.)

Vibration / Proximitor® Inputs. The VVIB card

provides a direct interface to seismic (velocity),

Proximitor®, Velomitor®, and accelerometer

(via charge amplifier) probes. In addition, DC

position inputs are available for axial measurements and Keyphasor® inputs are provided.

Displays show the 1X and unfiltered vibration

levels and the 1X vibration phase angle. -24vdc

is supplied from the control to each Proximitor

with current limiting per point. An optional termination board can be provided with active isolation amplifiers to buffer the sensor signals

from BNC connectors. These connectors can be

used to access real-time data by remote vibration analysis equipment. In addition, a direct

plug connection is available from the termination board to a Bently Nevada 3500 monitor.

The 16 vibration inputs, 8 DC position inputs,

and 2 Keyphasor inputs on the VVIB are divided between 2 TVIB termination boards for

3,000 rpm and 3,600 rpm applications. Faster

shaft speeds may require faster sampling rates

on the VVIB processor, resulting in reduced

vibration inputs from 16-to-8. (See Table 8.)

Three phase PT and CT monitoring. The VGEN

card serves a dual role as an interface for 3

phase PTs and 1 phase CTs as well as a specialized control for Power-Load Unbalance and

Early-Valve Actuation on large reheat steam turbines. The I/O interface is split between the

TGEN Termination Board for the PT and CT

inputs and the TRLY Termination Board for

relay outputs to the fast acting solenoids. 4-

20ma inputs are also provided on the TGEN for

monitoring pressure transducers. If an EX2000

Generator Excitation System is controlling the

generator, then 3 phase PT and CT data is communicated to the Mark VI on the network

rather than using the VGEN card. (See Table 9.)

Optical Pyrometer Inputs. The VPYR card moni

tors two LAND infrared pyrometers to create a

temperature profile of rotating turbine blades.

Separate, current limited +24Vdc and –24Vdc

sources are provided for each Pyrometer that

returns four 4-20ma inputs. Two Keyphasors are

used for the shaft reference. The VPYR and

matching TPYR support 5,100 rpm shaft speeds

and can be configured to monitor up to 92 buckets with 30 samples per bucket. (See Table 10.)

Operator Interface

The operator interface is commonly referred to

as the Human Machine Interface (HMI). It is a

PC with a Microsoft® Windows NT® operating

system supporting client/server capability, a

CIMPLICITY® graphics display system, a

Control System Toolbox for maintenance, and a

software interface for the Mark VI and other

control systems on the network. (See Figure 3.)

It can be applied as:

■ The primary operator interface for

one or multiple units

■

■ A backup operator interface to the

plant DCS operator interface

■ A gateway for communication links to

other control systems

■ A permanent or temporary

maintenance station

■ An engineer’s workstation

All control and protection is resident in the

Mark VI control, which allows the HMI to be a

non-essential component of the control system.

It can be reinitialized or replaced with the

process running with no impact on the control

system. The HMI communicates with the main

processor card in the Control Module via the

Ethernet based Unit Data Highway (UDH). All

analog and digital data in the Mark VI is accessible for HMI screens including the high resolution time tags for alarms and events.

System (process) alarms and diagnostics alarms

for fault conditions are time tagged at frame

rate (10/20/40 ms) in the Mark VI control and

transmitted to the HMI alarm management system. System events are time tagged at frame

rate, and Sequence of Events (SOE) for contact

inputs are time tagged at 1ms on the contact

input card in the Control Module. Alarms can

be sorted according to ID, Resource, Device,

Time, and Priority. Operators can add comments to alarm messages or link specific alarm

messages to supporting graphics.

Data is displayed in either English or Metric

engineering units with a one-second refresh

rate and a maximum of one second to repaint a

typical display graphic. Operator commands

can be issued by either incrementing / decrementing a setpoint or entering a numerical

value for the new setpoint. Responses to these

commands can be observed on the screen one

second from the time the command was issued.

Security for HMI users is important to restrict

access to certain maintenance functions such as

editors and tuning capability, and to limit certain operations. A system called “User

Accounts” is provided to limit access or use of

particular HMI features. This is done through

the Windows NT User Manager administration

program that supports five user account levels.

Software Maintenance Tools

The Mark VI is a fully programmable control

system. Application software is created from inhouse software automation tools which select

proven GE control and protection algorithms

and integrate them with the I/O, sequencing,

and displays for each application. A library of

software is provided with general-purpose

blocks, math blocks, macros, and application

specific blocks. It uses 32-bit floating point data

(IEEE-854) in a QNX operating system with

real-time applications, multitasking, prioritydriven preemptive scheduling, and fast context

switching.

Software frame rates of 10, 20, and 40 ms are

supported. This is the elapsed time that it takes

to read inputs, condition the inputs, execute

the application software, and send outputs.

Changes to the application software can be

made with password protection (5 levels) and

downloaded to the Control Module while the

process is running. All application software is

stored in the Control Module in non-volatile

flash memory.

Application software is executed sequentially

and represented in its dynamic state in a ladder

diagram format. Maintenance personnel can

add, delete, or change analog loops, sequencing logic, tuning constants, etc. Data points can

be selected and “dragged” on the screen from

one block to another to simplify editing. Other

features include logic forcing, analog forcing,

and trending at frame rate. Application software documentation is created directly from

the source code and printed at the site. This

includes the primary elementary diagram, I/O

assignments, the settings of tuning constants,

etc. The software maintenance tools (Control

System Toolbox) are available in the HMI and

as a separate software package for virtually any

Windows 95 or NT based PC. The same tools

are used for EX2000 Generator Excitation

Systems, and Static Starters. (See Figure 4 and

Figure 5.)

Communications

Communications are provided for internal data

transfer within a single Mark VI control; communications between Mark VI controls and

peer GE control systems; and external communications to remote systems such as a plant distributed control system (DCS).

The Unit Data Highway (UDH) is an Ethernetbased LAN with peer-to-peer communication

between Mark VI controls, EX2000 Generator

Excitation Controls, Static Starters, the GE

Fanuc family of PLC based controls, HMIs, and

Historians. The network uses Ethernet Global

Data (EGD) which is a message-based protocol

with support for sharing information with mul

ple nodes based on the UDP/IP standard

(RFC 768). Data can be transmitted Unicast,

Multicast or Broadcast to peer control systems.

Data (4K) can be shared with up to 10 nodes at

25Hz (40ms). A variety of other proprietary

protocols are used with EGD to optimize communication performance on the UDH.

40 ms is fast enough to close control loops on

the UDH; however, control loops are normally

closed within each unit control. Variations of

this exist, such as transmitting setpoints

between turbine controls and generator controls for voltage matching and var/power-factor

c

control. All trips between units are hardwired

even if the UDH is redundant.

The UDH communication driver is located on

the Main Processor Card in the Mark VI. This is

the same card that executes the turbine application software; therefore, there are no potential communication failure points between the

main turbine processor and other controls or

monitoring systems on the UDH. In TMR systems, there are three separate processor cards

executing identical application software from

identical databases. Two of the UDH drivers are

normally connected to one switch, and the

other UDH driver is connected to the other

switch in a star configuration. Network topologies conform to Ethernet IEEE 802.3 standards.

The GE networks are a Class “C” Private

Internet according to RFC 1918: Address

Allocation for Private Internets – February

1996. Internet Assigned Numbers Authority

(IANA) has reserved the following IP address

space 192.168.1.1: 192.168.255.255 (192.168/

16 prefix).

Communication links from the Mark VI to

remote computers can be implemented from

either an optional RS232 Modbus port on the

main processor card in Simplex systems, or

from a variety of communication drivers from

the HMI. When the HMI is used for the communication interface, an Ethernet card in the

HMI provides an interface to the UDH, and a

second Ethernet card provides an interface to

the remote computer.

All operator commands that can be issued from

an HMI can be issued from a remote computer

through the HMI(s) to the Mark VI(s), and the

remote computer can monitor any application

software data in the Mark VI(s). Approximately

500 data points per control are of interest to a

plant control system; however, about 1,200