presentation esp grounding
TRANSCRIPT
Stopping OilfieldLightning Damage
You can not stop lightning!
True. But you can stop the damage it does!
An Engineering Approach
Oil Production Priorities
• Tank Batteries, does NFPA 780 really apply?
• Disposal pump motors and controls• Electric Submersible Pumps, ESP,
does API RP11S really apply?• ESP Variable Frequency Drives• Pumping unit motors and controls
Tank Battery Protection
• Strike Collection – with Franklin rods (Also called lightning rods, air terminals, etc.), catenary wires, early streamer emitters
• National Fire Protection Association (NFPA) and Lightning Protection Institute
• Strike Avoidance – Charge Transfer Systems
Electrical Equipment Protection
• 4-wire Transient Voltage Surge Suppressors (TVSS)
• Wellhead Grounding• Junction box TVSS mounting• Ungrounded transformer windings• Separate Ground Wires• Power distribution with an overhead
neutral, OHN, or shield wire
Tank Battery Protection
CL VSD
125 HP SWD Motor
Oil Storage300 Barrel12' dia, 15'-5" highSteel Each
catw
alk
Knockouts, steel10' dia x 20' long &10' dia x 15' long
Disposal Well150' East
Nort
h
500 HP SWD Motor
catwalk
Rolling Sphere Calculation
74 foot diameter
Scale 1" = 20'
Each, 1000 Barrels15'-5" dia, 30' highFiber glass, gun barrel, water sep.
Vertical Gas Separator3' dia x 12' high
Problems
• Presence of explosive gases• Fluids that develop an electrical charge• Attracting lightning and getting it safely
into the ground without igniting gases• Does NFPA 780 really apply?
Solution
• Prevent lightning from striking tank batteries
• Charge Transfer Systems - -Explanation Demonstration
• Details !! The devil is in the…………….. MIL TFP 41
Leader Delayed by Space Charge
Competing Leaders Continue toward
Earth
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Winning the Competition
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GroundingMaking Contact with Charge
beneath the tanks and in the tanks
• Ground rods, loops, grids• Chemical grounds• Thief hatch ground rods• Carbon C Veil• Bonding
ElectricalEquipmentProtection
Metal Oxide Varistors (MOV) TVSS (SPD) Basic Element
• Varistor = variable resistor• Resistance changes with voltage• Convert lightning energy into heat, if
properly installed• Analogous to Back Pressure Relief Valve
Current or Flow
Pres
sure
or
Vol
tage
Lim
it
Max
imum
Allo
wab
le W
orki
ng P
ress
ure
o
r In
sula
tion
Punc
ture
Vol
tage
Pressure or VoltsX
+Volts-
Current
MOV
TVSS Modes and Wires
deltaA B
C
G
A B
YThree Mode
G
A B
C
A
C G
Four Mode Six Mode
B
C
3-wire SPD (TVSS), No Ground
Effect of Long Ground Wire
Large pressure dropin long, small diameterdischarge pipe.
Pressure Relief Valve
MOV
Large voltagedrop alongground wireinductance
Voltage Impulse Pressure Impulse
Valve bypass into a small diameter discharge tube equivalent to a TVSS with long ground wire and high
ground resistance.
Wellhead Grounding
• Getting to Infinite Ground – water table?• A ground rod thousands of feet long• Ground resistance less than ONE ohm• Can the wellhead be damage by lightning?• National Electric Code (NEC) requirement
Opus 250, No. .-112M• Corrosion? AC – No, Cathodic protection
evaluation – CPET. Coexistence – Surge and Cathodic protection
Wellhead Electrical Connection
• Ground Clamps – loose, loose wire, paint and corrosion, few contact points, shock, workover crew removal and replacement?
• Cad Weld – Great connection, RR signal lights & substation ground grids, can not be removed to check wires, welding around natural gas?
• Service Post Grounding
Service Post Wellhead Grounding
Welded Bolt and Ground Lug
H1H2
H1 H1H2 H2
X1 X2 X1 X1X2 X2
Pole Butt Plate or Wrap
Transformers
Lightning Arresters
Additional groundrods as needed
Switchboard
Ground connection point
Junction orVent Box
Earth surface line
Power SystemGround
ESP Cable
Ground wire
armor ground wire
Wellhead
Wellheadgroundresistance
Inductance of pole ground wire
Inductance of pole towellhead ground wire
Butt wrapgroundresistance
0 V
10,000 V
+
Lightning atarrestercommon
Voltage at wellhead
Voltage at switchboard
Infinite Ground
Ground Wire and Wellhead Voltages
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
0.E+00 1.E-06 2.E-06 3.E-06 4.E-06 5.E-06 6.E-06 7.E-06
Time
Vo
lts
.5 Ohm5 Ohm10 Ohm20 Ohm a b c
g
gSwitchboard Mounted TVSS
a b c
Vent BoxMounted TVSS
MOV Volt Amp CharacteristicsCurrent
Volts+MOV volts
-MOV volts
Backwards
MOVvolts
G
A
B
C
MOVvolts
+ _
Lightning voltage on butt wrap
Separate Bonded Ground Wires
An Improperly Installed TVSS Can Cause ESP Damage
Indian Basin and Tatum, NM
H1H2
X1 X2 X1 X1X2 X2
Transformers
Lightning Arresters
Shield Wire(Overhead Neutral, OHN)
TVSS
H2 H2H1 H1
Reda
Cab
le
• Backward Through:
• Lightning Arresters• TVSS or Secondary Lightning
Arresters• Switchboard Mounted TVSS
H1H2
H1 H1H2 H2
X1 X2 X1 X1X2 X2
Wellhead
Switchboard
Pole Butt Plate or Wrap
Preferred Submersible Pump Grounding for Lightning Protection
Ground connection point
Junction orVent Box
a b c
g
1. Ground wires should be green THHN insulated, #2AWG stranded copper to minimizebreakage and corrosion. 2. For safety ESP cable armor must be connected to the ESP System Ground with
Transformers
Lightning Arresters#8 AWG solid copper wire as shown. Between the switchboard and poles it should beisolated from the Power System Ground. 3. Power System and ESP System ground wires should be run no closer than 6" apartto avoid sideflash. Pole ground wire and wellhead are the only permissible connectionson the Power System ground wire.
Pro-MoDr TVSS
6. A service post (Burndy K2C23B1 or Penn-Union SCS-4A1) screwed into a tapped hole between bolts in the lower flange is the recommended wellhead grounding method. A "hot work" permit will be required if natural gas is present. Connection at the lower flange should eliminate the need for groundwire removal during a workover.
Earth surface lineESP Cable
Additional groundrods as needed
4. ESP System Ground wires should connect to the ground lug on the TVSS at the junction box. The small green TVSS wire should ground the junction box internally. 5. At the junction box armors should not come in contact with each other or the metalbox to minimize ground loop interference.
ESP SystemGround, BlueTape
Power SystemGround, WhiteTape
H1H2
H1 H1H2 H2
X1 X2 X1 X1X2 X2
Wellhead
Switchboard
Pole Butt Plate or Wrap
Ground connection point
Junction orVent Box
a b c
g
Lightning Arresters
Pro-MoDr TVSS
Earth surface lineESP Cable
Additional groundrods as needed
Cable armor grounds
Armorground
Simplified Submersible Pump Grounding for Lightning Protection
1. Transformer windings to the ESP must be ungrounded.2. Power System Ground connects to the switchboard and cable armors as shown.3. Power System Ground goes directly to the wellhead without contacting the junction box.4. TVSS and Power System ground wires should be green THHN insulated, #2 AWG strandedcopper to minimize breakage and corrosion and isolated from each other to avoid sideflash.5. At the junction box armors should not come in contact with each other or the metal box.6. TVSS Ground wire should connect to the ground lug on the TVSS at the junction box.The small green TVSS wire grounds the junction box internally. 7. A service post (Burndy K2C23B1 or Penn-Union SCS-4A1) screwed into a tapped hole between bolts in the lower flange is the recommended wellhead grounding method. A "hot work" permit will be required if natural gas is present. Connection at the lower flange eliminates the need for groundwire removal during a workover.
Transformers(secondary windings ungrounded)
Power SystemGround - White& Red Tape
TVSS Ground Blue Tape
TVSS2
H1H2
H1 H1H2 H2
X1 X2 X1 X1X2 X2
Pole Butt Plate or Wrap
Transformers
Lightning Arresters
Additional groundrods as needed
Earth surface line
Power SystemGround
Disc
onne
ct
Variable Speed Drive
ESP Cable
Ground connection point
Wellhead
or
Step-Up Transformer
TVSS
1
Preferred Submersible PumpLightning Protection Grounding for Variable Speed Drives
1. Ground wires should be green THHN insulated, #2AWG stranded copper to minimizebreakage and corrosion. 2. Power system ground wire should not connect directly to the drive through conduitor the disconnect. It should go directly to the wellhead. This is critical to preventing TVSS1 from damaging the VSD and ESP when lightning strikes. Disconnect,VSD and step-up transformers are still bonded via the ESP system ground wire. 3. 480V power into VSD should be ungrounded. 4. For safety ESP cable armor must be connected to the ESP System Ground or TVSSGround with #8 AWG solid copper wire as shown. Between the switchboard and poles it should be isolated from the Power System Ground.
6. TVSS Ground wire should connect to the ground lug on the side of TVSS2 at the junction box. The small green TVSS wire should ground the junction box internally.
5. Power System, ESP System and TVSS ground wires should be isolated from each other to avoid sideflash
7. At the junction box armors should not come in contact with each other or the metalbox to minimize ground loop interference. 8. A service post (Burndy K2C23B1 or Penn-Union SCS-4A1) screwed into a tapped hole between bolts in the lower flange is the recommended wellhead grounding method. A "hot work" permit will be required if natural gas is
present. Connection at the lower flange should eliminatethe need for ground wire removal during a workover. 9. If drive is trailer mounted junction box shouldbe fiber glass for electrical isolation
Junction orVent Box
armor groundwire
Power system groundwhite tape
ESP system groundred tape
TVSS ground blue tapearmor ground wire
Ungrounded Transformer Windings
• The preferred way for 80 years• Continuous oil production through first
insulation fault• Grounding will damage cable or motor on
first fault so that ESP must be pulled• Improved lightning protection – Grounding
is to LA common• Perfectly Safe
Junction Box Mounting
• Shortest ground wire to the wellhead• On load side of switchboard contactor so
overload protection will be activated if TVSS fails
• Wellhead connects directly to the housing of the downhole ESP motor
Priority 2 – Protection of Disposal Pump Motor and Control
• A Wellhead ground is normally not available
• Connect to ground loop around tank battery
• If possible separate lightning arrester ground wire from motor and control ground wire
Ground rod (Optional)
Control box
Ground wires
TVSS
Motor Wellhead
480V, 3 phase
YEarth surface
XZ
Pow
er S
yste
m G
roun
d an
dLi
ghtn
ing
Arr
este
r Com
mon
Summary
• Charge Transfer Systems can provide improved tank battery protection. Reliability has been over 99% for 40,00 service years
• Properly designed and installed TVSS can prevent almost all equipment damage if: 4-wire TVSS are used grounded to wellhead junction box mounting ungrounded transformer windings separate ground wires
Lightning Damage can be Stopped!Science and Engineering will Ultimately Prevail
Equipment Repair and Replacement can be Reduced
Lost Production can be Minimized
A Bad Day in the Neighborhood