jks ground fault testing march 2015 juan carlos gonzalez
TRANSCRIPT
SHANGHAI. IN-HOUSE SEMINAR Ground fault MARCH 8TH, 2015
Juan Carlos Gonzalez, Sr Technical Manager [email protected]
p: +41 791921579
GROUND FAULT. ONSITE ISOLATION
MEASUREMENTS
2 www.jinkosolar.com
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Onsite insulation measurement for PV arrays Introduction
DC
AC
IN A FLOATING SYSTEM NO LIVES PARTS SHOULD BE ACCESIBLE OR HAVE DIRECT CONTACT BETWEEN LIVE AND NON-CURRENT-CARRYING METAL PARTS
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Onsite insulation measurement for PV arrays
• Humidity
• Changes in temperature
• UV
• Mechanical stress
MAIN FACTORS AFFECTING THE ISOLATION PROPERTIES
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Onsite insulation measurement for PV arrays
IN THE EVENT OF AN INSULATION FAULT, THE ELECTRICAL RESISTANCE (RISO) DROPS DRIVING A LEAKAGE CURRENT THROUGH THE GROUND CONNECTION FROM THE FAULTY POINT
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“Renewable Energy, Reliable and efficient use of the power of the nature”, Bender
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Onsite insulation measurement for PV array
• Backsheet (scratches, bubbles, aging…)
• Cables in module or from string to inverter,…(insulation damages, aging, mechanical stress,…)
• Connectors and junction boxes (IP index affected, aging, bad connection,…)
• EVA adhesion (bubbles allowing moisture ingress and forming electrical path between busbars and frame)
• String boxes (aging, bad connection, IP index affected,…)
• Inverter
DIELECTRIC COMPONENTS PRONE TO FAIL
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Onsite insulation measurement for PV array
IEC61215 Standard
• Minimum insulation resistance 40MΩm2
• (1650mmx992mm = 1.636 m2) = 40MΩm2 /1.636 m2 = 24.45MΩ
JKM/JKMS P60/PP60/PP60+
• (1956mmx992mm = 1.94 m2) = 40MΩm2 /1.94 m2 = 20.62MΩ
JKM/JKMS P72/PP72/PP72+
• BEFORE STARTING TO WORK. INSULATION RESISTANCE > 1KΩ/V (500KΩ AS MIN. BEFORE CONNECTION TO GRID)
TRANSFORMERLESS INVERTER
• CONTINUOUS MONITORING
GALVANIC ISOLATION
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Onsite insulation measurement for PV arrays
IEC61215 and VDE 0126-1-1
• RISK OF INCOMPATIBILITY DEPENDING ON THE CHARACTERISTICS OF THE INSTALLATION
• GFD THRESHOLD ALARM > THAN ARRAY ISOLATION VALUE
𝑅𝑖𝑠𝑜 𝑎𝑟𝑟𝑎𝑦 =1
1𝑅𝑖𝑠𝑜 𝑚𝑜𝑑𝑢𝑙𝑒 1
+1
𝑅𝑖𝑠𝑜 𝑚𝑜𝑑𝑢𝑙𝑒 2+
1𝑅𝑖𝑠𝑜 𝑚𝑜𝑑𝑢𝑙𝑒 3
+ ⋯ +1
𝑅𝑖𝑠𝑜 𝑚𝑜𝑑𝑢𝑙𝑒 𝑛
𝑅𝑖𝑠𝑜 𝑎𝑟𝑟𝑎𝑦 =𝑅𝑚𝑜𝑑𝑢𝑙𝑒
𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑚𝑜𝑑𝑢𝑙𝑒𝑠 For modules with same area
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Onsite insulation measurement for PV arrays Some topics to look at
INSULATION RESISTANCE VARIABILITY (Ω)
Temperature
Humidity Array
dimensions
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Onsite insulation measurement for PV arrays Some topics to look at
METHODS FOR INSULATION
MEASUREMENT
POLES SHORT-CIRCUITED
POLE BY POLE
ISOLATION METER OR MEGGER (COMMERCIAL NAME)
Follow the general rules of safety tagging the relevant apparatus of the installation
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Onsite insulation measurement for PV arrays Some topics to look at
STRATEGY BY REDUCTION
SWITCH OFF THE INVERTER OF
THE SUBCIRCUIT TO BE
MEASURED
OPEN THE SWITCHES
INVOLVED IN THE CIRCUIT TO BE MEASURED
REMOVE OR DISCONNECT
THE OVERVOLTAGE PROTECTION
DEVICES BEFORE THE TEST
SUB-CIRCUIT TO BE MEASURED
MUST BE ISOLATED FROM THE REST OF THE
INSTALLATION
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Onsite insulation measurement for PV arrays Some topics to look at
STRING INVERTER OR INVERTER W/O STRING
BOXES
Disconnect all of the inputs except one
Check if it works properly
Connect and disconnect each string until the
alarm appears
The test can be performed without insulation meter as a first approach
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Onsite insulation measurement for PV arrays Some topics to look at
With several string boxes
Open all the switches of the string boxes except
for one string box
Check if it works properly
Connect and disconnect each string box until the
problem appears
Once the string box is isolated, proceed as
with 1 string box
With one string box Open the fuse holders for all the strings except for
one Check if it works properly
Connect and disconnect each input until the alarm
appears
CENTRAL INVERTER OR
INVERTER WITH DC STRING BOXES
The test can be performed without insulation meter as a first approach
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Onsite insulation measurement for PV arrays Some topics to look at
ONCE THE STRING OR AREA HAS BEEN REDUCED
MEASUREMENT OF THE ISOLATION BY MEANS OF A MEGGER MODULE
BY MODULE
ONCE THE MODULE/S HAS/HAVE BEEN IDENTIFIED
DISCONNECT THE CABLES FROM THE JB TO IDENTIFY ORIGIN IN
LAMINATION/CABLE+CONNECTOR
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Onsite insulation measurement for PV arrays Some topics to look at
DC
AC
String box
Intermitent failures
• Moisture ingress in a module
• After some raining days ( cable drains, junction boxes, string boxes or inverters)