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Triconex CorporationTriconex Corporation
System System GroundingGrounding
TRICON HardwareTRICON Hardware
Electrical systems must be connected to ground in order to:
Protect personnel from electric shock.Protect personnel from electric shock.Protect equipment from damage.Protect equipment from damage.Protect the site from lightning damage.Protect the site from lightning damage.Ensure the reliability and electrical integrity of the Ensure the reliability and electrical integrity of the system.system.To have interference free operationTo have interference free operation
What is Ground?What is Ground?It is a connection to the earth, or to something used It is a connection to the earth, or to something used in place of the earth.in place of the earth.
Why do we require a ground?Why do we require a ground?The ground is required as it is used to establish and The ground is required as it is used to establish and maintain the potential of the earth.maintain the potential of the earth.
TRICON System typically utilizes three (3) separate ground references:
AC safety or chassis ground (protective earth ground) - TRICON Chassis Ground
Signal or Instrument (or Master Reference) ground - TRICON Signal Ground (TSG)
Field loop shield ground
AC Safety ground is applied to each chassis
Signal or Instrument (or Master Reference) ground is the field loop power supply return
Field loop shield ground is for referencing instrument loop wiring shields typically to instrument or Master Reference ground
TRICONTRICONMainMain
ChassisChassis
AC Safety Ground Bar
TRICONTRICONExpansionExpansionChassisChassis
Each chassis Each chassis MUST BEMUST BEconnected to AC Safety connected to AC Safety ground to ensure personnel ground to ensure personnel safety!safety!
TRICONTRICONExpansionExpansionChassisChassis
TRICONTRICONChassisChassis
AC Safety Ground BarAC Safety Ground Bar
Each V5 Each V5 -- V8 Digital I/O V8 Digital I/O Term Panel Term Panel MUST BEMUST BEconnected to AC Safety connected to AC Safety ground to ensure personnel ground to ensure personnel safety!safety!
Digital Input TermDigital Input Term
AC Safety Ground MUST be applied to each chassis (Main, Expansion & RXM) regardless of floating or non-floating systems.
AC Safety Ground MUST be applied to each V5 -V8 DI/DO Term Panel. (floating/non-floating) as the V5 - V8 I/O ELCO cables do not have a connecting wire to chassis. Connection to AC Safety Ground for V9 Terms are not required.
AC Safety Ground MUST NOT be applied to AI/AO Term Panels and #3504E.
AC Safety Ground Analog SystemAC Safety Ground Analog System
AC SafetyAC Safety
TRICONTRICONChassisChassis
Isolated +24Isolated +24Power SupplyPower Supply
V+V+ VV--
Analog Input TermAnalog Input Term
Once VOnce V-- is connected to a is connected to a AI/AO Term Panel, it is AI/AO Term Panel, it is connected to the internal connected to the internal TRICON Signal Ground TRICON Signal Ground (TSG).(TSG).
If the TRICON RC Clip is If the TRICON RC Clip is installedinstalled, TSG is connected , TSG is connected to AC Safety Ground via a to AC Safety Ground via a parallel resistor/capacitor parallel resistor/capacitor circuit.circuit.
TSG VTSG V-- is referenced to AC is referenced to AC Safety within Safety within millivoltsmillivoltsrange.range.
Dedicated Ground Analog SystemDedicated Ground Analog System
If the TRICON RC Clip is If the TRICON RC Clip is removed, TSG is removed, TSG is disconnected from AC disconnected from AC Safety Ground. Safety Ground.
TSG TSG MUST BEMUST BE connected connected to a dedicated ground. to a dedicated ground.
One connection is required One connection is required and is completed at the and is completed at the Main Chassis location Main Chassis location & any & any remote RXM locations.remote RXM locations.
The dedicated ground is The dedicated ground is typically considered a quiet typically considered a quiet earth ground or DCS earth ground or DCS Master Reference Ground.Master Reference Ground.
Isolated +24Isolated +24Power SupplyPower Supply
V+V+ VV--TRICONTRICONChassisChassis
Analog Input TermsAnalog Input Terms
Dedicated GroundDedicated Ground
AC SafetyAC Safety
Dedicated Ground Analog SystemDedicated Ground Analog System
AC SafetyAC Safety
Dedicated GroundDedicated Ground
Field loop wiring shields Field loop wiring shields are typically connected to are typically connected to TRICON Term Panels. TRICON Term Panels.
The TRICON Term Panel The TRICON Term Panel shield ground screws shield ground screws should be tied to should be tied to instrument ground or the instrument ground or the dedicated ground. dedicated ground.
TRICONTRICONChassisChassis
Isolated +24Isolated +24Power SupplyPower Supply
V+V+ VV--
Analog Input TermsAnalog Input Terms
TRIOCN RC network TRIOCN RC network
V5 V5 -- V8 SystemV8 System
#8300/#8301/#8305/#8306 TRICON Power #8300/#8301/#8305/#8306 TRICON Power Modules are equipped with a simple RC network Modules are equipped with a simple RC network connected between the signal and chassis groundconnected between the signal and chassis ground
#8300A/#8301A/#8305A/#8306A TRICON Power #8300A/#8301A/#8305A/#8306A TRICON Power Modules allows one to disconnect the internal RC Modules allows one to disconnect the internal RC network and directly access the TRICON signal network and directly access the TRICON signal ground.ground.
TRIOCN RC network TRIOCN RC network
V9 SystemV9 System
The RC network is external to the TRICON Power The RC network is external to the TRICON Power Modules.Modules.
TRIOCN RC networkTRIOCN RC network
StandStand--Alone DigitalAlone Digital--Only SystemOnly System
Connecting the RC jumper will be sufficient
StandStand--Alone AnalogAlone Analog--Only or Mixed Only or Mixed Analog/Digital SystemAnalog/Digital System
Connecting the RC jumper will be sufficient
TRIOCN RC networkTRIOCN RC network
Integration with DCSIntegration with DCS
If TRICON is a stand-alone digital-only system, connection of the RC jumper (at the power module for V5 to V8) is sufficient
If TRICON is a stand-alone analog-only or mixed analog/digital system, a single connection must be made between TRICON signal ground and the common tie point of the DCS signal ground
A TriStation Link with model #410x ICM/EICM may cause a problem if the TriStation PC does not share the safety ground connection as the TRICON.
Exercise caution especially if the TRICON and the DCS are physically separated or reside in separate buildings. The same problem could also occur with any RS232 connection including anyMODBUS connections.
Connecting two pieces of equipment located in Connecting two pieces of equipment located in different buildingsdifferent buildingsTRICON I/O bus RSTRICON I/O bus RS--485 connection 485 connection extended beyond the control room.extended beyond the control room.Current flow via the Shield ground which is Current flow via the Shield ground which is not held at a constant, nonnot held at a constant, non--varying voltage.varying voltage.Implementing a “floating” ground system.Implementing a “floating” ground system.
In most industrial control systems, the return side In most industrial control systems, the return side of the field power supply is directly connected to of the field power supply is directly connected to earth.earth.
Emergency Shutdown (ESD) and Fire & Gas Emergency Shutdown (ESD) and Fire & Gas detection applications very often require the detection applications very often require the I/O system to be "floating".I/O system to be "floating".
In a floating ground system, the field power In a floating ground system, the field power supply is not directly connected to earth supply is not directly connected to earth ground , but is connected to an artificial ground , but is connected to an artificial ground which can be created with a highground which can be created with a high--impedance resistor voltage divider.impedance resistor voltage divider.
24VDC POWERSUPPLY UNIT
+-
24VDC POWERSUPPLY UNIT
+-
EARTH GROUND
TO ETP POWER
24VDC
0VDCR1
R2
The main use of a floating ground system with a The main use of a floating ground system with a suitable Ground Fault Detector allows for the suitable Ground Fault Detector allows for the implementation of a "noimplementation of a "no--fail system".fail system".
A “noA “no--fail system” is faultfail system” is fault--tolerant of any tolerant of any singlesinglefieldfield--wiring fault to earth ground.wiring fault to earth ground.
These ground faults should be detectable by These ground faults should be detectable by the GFD, and if repaired in a timely manner, a the GFD, and if repaired in a timely manner, a shutdown or disturbance to the application shutdown or disturbance to the application should be avoided.should be avoided.
The main purpose of a GFD is to detect the The main purpose of a GFD is to detect the presence of an unintentional connection to presence of an unintentional connection to earth ground, other than that of the fixed earth ground, other than that of the fixed highhigh--impedance connection.impedance connection.
A GFD should provide some means of alarming A GFD should provide some means of alarming upon detecting an ground fault.upon detecting an ground fault.
The HOLEC GFD has a sensitivity of 20mA The HOLEC GFD has a sensitivity of 20mA minimum (between +minimum (between +veve and and --veve), when used with ), when used with an external 1.2kan external 1.2kΩ resistor divider in 24VDC resistor divider in 24VDC applications.applications.
24VDC POWERSUPPLY UNIT
+-
24VDC POWERSUPPLY UNIT
+-
EARTH GROUND
HOLEC
+
-R1
R2
It is common to install multiple It is common to install multiple GFDsGFDs in a in a system, either one per Marshalling system, either one per Marshalling Cabinet or one per termination panel. Cabinet or one per termination panel. After a ground fault has been detected, After a ground fault has been detected, only the field wiring of the points only the field wiring of the points attached to the alarmed GFD needs to be attached to the alarmed GFD needs to be searched for the earth short.searched for the earth short.
Ground Fault Detection with D.I. ModuleGround Fault Detection with D.I. Module
EARTH GROUND
R1
R2
HOLEC
24VDC
0VDC
PS+PS-
+-
DI ETP
DI MODULE
Ground Fault Detection with D.I. ModuleGround Fault Detection with D.I. Module
The following limitations apply to the use The following limitations apply to the use ofof GFDsGFDs with digital inputswith digital inputs::A GFD always detects ground faults on A GFD always detects ground faults on the positive side of the contact.the positive side of the contact.A GFD always detects ground faults on A GFD always detects ground faults on the negative side of the contact when the the negative side of the contact when the contact is closed. When the contact is contact is closed. When the contact is open, the GFD might not detect the fault.open, the GFD might not detect the fault.
Ground Fault Detection with D.I. ModuleGround Fault Detection with D.I. Module
When the contact is open, the impedance When the contact is open, the impedance of the input circuitry is in series with the of the input circuitry is in series with the fault impedance. fault impedance. If the sum of the impedances exceeds If the sum of the impedances exceeds the sensitivity of the GFD, then the GFD the sensitivity of the GFD, then the GFD might not detect the fault.might not detect the fault.
Ground Fault Detection with D.O. ModuleGround Fault Detection with D.O. Module
EARTH GROUND
R1
R2
HOLEC
24VDC
0VDC
PS+PS-
+-
DO ETP
FROM DOMODULE
Ground Fault Detection with D.O. ModuleGround Fault Detection with D.O. Module
The following limitations apply to the use The following limitations apply to the use ofof GFDsGFDs with digital outputs:with digital outputs:A GFD always detects ground faults on A GFD always detects ground faults on
the negative side of the load.the negative side of the load.A GFD always detects ground faults on A GFD always detects ground faults on
the positive side of the load when the the positive side of the load when the load is energized. When deload is energized. When de--energized, a energized, a GFD might not detect the fault.GFD might not detect the fault.
Ground Fault Detection with D.O. ModuleGround Fault Detection with D.O. Module
When deWhen de--energized, the impedance of the energized, the impedance of the load is in series with the fault impedance. load is in series with the fault impedance. If the sum of the impedances exceeds If the sum of the impedances exceeds the sensitivity of the GFD, then the GFD the sensitivity of the GFD, then the GFD might not detect the fault.might not detect the fault.
Ground Fault Detection with A.I. ModuleGround Fault Detection with A.I. Module
EARTH GROUND
R1
R2
HOLEC
24VDC
0VDC
PS+PS-
+-
AI ETP
Tx250
180
Ground Fault Detection with A.I. ModuleGround Fault Detection with A.I. Module
From test results and the electrical From test results and the electrical circuit analysis, we confirmed that the circuit analysis, we confirmed that the accuracy degradation in the presence of a accuracy degradation in the presence of a ground fault is inherent in any 4ground fault is inherent in any 4--20mA 20mA instumentation instumentation loops.loops.
TRICONEXTRICONEXYour supplier for all Your supplier for all
your Safety and Critical your Safety and Critical Control NeedsControl Needs
DefectsDown TimeFalse Trips
BACKPLANE8-POINT ANALOG OUTPUT MODULE
PWRA (22A)
RTN (22E)
PWRB (24A)
CABLE
SelectorLogic
DAC
TERMINATIONPANEL
RTN (24E)
OUT1 (2A)
RTN1 (2E)
SelectorLogic
DAC
SelectorLogic
DAC
Loop power
Currentloopback
Currentloopback
Currentloopback
A
B
C
32-POINT ANALOG INPUT MODULESBACKPLANECABLE
tospa re
TERMINATION PANEL
Is ola tion/filte ring
ADCAmp1
32
Mux
Hi-Ref
Low-Ref
ADCAmp1
32
Mux
Hi-Ref
Low-Ref
ADCAmp1
32
Mux
Hi-Ref
Low-Ref
PS 1
PS 2
PS 1
PS 2
toothe rpoints
180 ohms
Note 3
Types of PowerUtility PowerMains PowerUPSCleanFloatingAC / DC
Types of Earth ConnectionClean EarthDirty EarthUtility EarthLow noiseSystemComputer
Basically on two types ofGround :-a) AC - dirtyb) DC - clean
System earthInstrument earth
EMCElectromagnetic Compatibility-> Started by the military application 15 yrs ago
Use 3 core power cables for optimal line filteringPower source is reference to earthFloating power contains much more noise than earth referenceFloating power needs isolation transformerFloating power may drift to any common mode potential
Line filtering requires earth connectionImpedance if 3 core power is 100 ohms
I/A designed by National Electrical Code
Normal and Common mode signals by : potential equalisationGalvanic isolationShieldingEnclosures
Signal to noise ratio
GROUNDING the TRICONGROUNDING the TRICON
Expansion Chassis
(Protective Earth)
ACSAFETYGROUND
1/4" Bolt on left side of each chassis
Main Chassis
Expansion Chassis
AC Safety GroundBus Bar