2018/10/24 1 2018/10/24 2 SAFE DEAD WORK SAFE DEAD WORK.. What - PowerPoint PPT Presentation

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SAFE DEAD WORK • “SAFE DEAD WORK”………….. What is this? • There are two practical options….. • NRS 097-2-1 compliance (switch off and break before you make) • What is the Dead Grid Safety Lock? • How does the Dead Grid Safety Lock work? • Is installation net-energy throttling functions as a safety feature?

Electrical Installation Regulations Point of Supply Point of Control

Two Points of Supply EG Utility Point of Point of Supply Supply

LV Dead - Safe Work Practice • Identify circuit • Open circuit • Isolate circuit • Tag circuit • Lock out circuit • ( DO NOT USE EARTHING & BONDING ) • Test at location • Work 7

Locked Out and Tagged

Typical LV Locking and Tagging Equipment 2018/10/24 9

Test to Proof Voltage = 0 Volt = Safe 2018/10/24 10

Single Customers per MV-LV Transformer • Employ standard LV safe procedure as given above: • I.e. Isolation of the installation 2018/10/24 11

Multi-Customer LV Networks Complex and Impossible to Employ the normal safe work procedure 2018/10/24 12

Typical Over Head LV Networks 2018/10/24 13

Where are the EG ? The only feasible Approach: Secure - Automated Safety Systems 2018/10/24 14

How do we automate this? Contactor NO CUSTOMER UTILITY INSTALLATION NETWORK C With the Utility side dead, a live EG cannot feed power back Simple example of one embodiment of the principle. 2018/10/24 15

Automated LV Safe Work Practice • Normal upstream safety procedure • Test at location + Automated Dead-Grid Lock • Work 16

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Dead-Grid Lock The Purpose of the DEAD-GRID LOCK is to ensure that power cannot flow back from a EG once a utility worker has proofed that this part of the LV network is safe to work on. It relies on the EG to power down automatically when the utility power fails. ( Anti-islanding and out of bounds requirements)

Dead-Grid Lock If this does not happen, the safe work procedure will detect the condition and further steps is to be taken to make the installation safe. The sole purpose of this device is to secure that once the network is proven to be safe to work on- that it remains so, regardless of any actions or failure of equipment during this time on the EG’s side.

Test to Proof Voltage = 0 Volt The Critical Step : Test – once dead AND Utility supply locked out – The automatic Dead Grid Safety Lock ensures safety from the EG’s side. 2018/10/24 20

Dead-Grid Safety-Lock AC Disconnector On / Off Cable to EG

Dead-Grid Safety-Lock 2018/10/24 22

DGSL Installation on a PV Inverter Main DB Connection PV String Installation 8.9 kVA On PF .98 DC side Arresters Inverter

Safe Even when it is DEAD 24

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LV Live - Safe Work Practice 2018/10/24 26

Multi customer feeder - Minimum Safety Requirements POS MAIN DB EG - DB Structural lighting protection and POC bonding of PV panels PE PE Locked in Grid-Tied-Mode