SHANGHAI. IN-HOUSE SEMINAR Ground fault MARCH 8TH, 2015

Juan Carlos Gonzalez, Sr Technical Manager jcarlos.gonzalez@jinkosolar.com

p: +41 791921579

GROUND FAULT. ONSITE ISOLATION

MEASUREMENTS

2 www.jinkosolar.com

3

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

4

Onsite insulation measurement for PV arrays

• Humidity

• Changes in temperature

• UV

• Mechanical stress

MAIN FACTORS AFFECTING THE ISOLATION PROPERTIES

5

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

1 2 3

“Renewable Energy, Reliable and efficient use of the power of the nature”, Bender

6

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

7

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

8

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

9

Onsite insulation measurement for PV arrays Some topics to look at

INSULATION RESISTANCE VARIABILITY (Ω)

Temperature

Humidity Array

dimensions

10

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

11

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

12

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

13

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

14

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

15

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)