Safety during Hardware Commissioning ELQA Activities Davide Bozzini on behalf of the ELQA teamAT/MEL-EM 18th October 2007
ELQA during Hardware Commissioning • Tasks • Electrical qualification of each superconducting circuit, including the current leads and the active systems connected to the circuit. • Measurement of electrical parameters of each superconducting circuit in order to define reference values for the initial operation of the power converters and for the machine operation. • Verification of the integrity of the instrumentation used for the protection of the superconducting magnets and current leads. • Objectives • Release each individual superconducting circuit for powering, • Collect all the necessary electrical parameters for operation. • Trace all the data acquired. • Manage the related non conformities. • Apply the highest level of safety for personnel and equipment
Description of the ELQA tests I See details in LHC-DE-TP-0007 rev 0.1 • ORC OHMIC RESISTANCE • The resistance of a circuit is measured between the two current leads. Maximum current 6 A, maximum voltage 30 V DC. • HVQ HIGH VOLTAGE QUALIFICATION • Each circuit is energized individually with respect to ground using a DC voltage source limited to a current of 2 mA during charging. The maximum voltage applied is 1.9 kV DC.
Description of the ELQA tests II • TFM TRANSFER FUNCTION OF THE IMPEDANCE • This measurement determines the impedance as a function of frequency. The impedance is measured at the level of the current leads by applying a sinusoidal signal with maximum amplitude of 10 V within a frequency range of 0.1 Hz - 10 kHz. • ICC CONTINUITY OF INSTRUMENTATION • Verifies that the instrumentation for the current lead protection and the global circuit protection are placed at the right position and are routed to the right connectors and pins. Certifies the absence of broken or disconnected instrumentation wires after the cool-down. A DC current of less than 6 A and maximum 30V is applied. • DPC DIODE POLARITY CHECK • Proves that none of the protection diodes in the three main circuits (MB, MQF and MQD) is reversed. A DC current of less than 6 A is put throughout the circuit, the maximum voltage is less of 150 V.
High voltage qualification HVQ • During this tests, voltages up to 1.9 kV dc are applied between circuits and ground. • The powered circuit (mainly capacitance versus ground) becomes a second generator as soon as it gets energy stored. • The HVQ equipment is connected to the live parts of current leads with specific crocodile connectors IP00. This means that live parts are accessible! • How we proceed to increase the safety level during this test • Complete test of the circuits belonging to a electrical safety subsector is fully automatic. • After PC switch off and after the warm cable disconnection, all circuits are temporary grounded on the superconducting side. Here we touch the live parts! • All circuits are manually connected to a HVQ rack. The circuits are grounded via this rack. • The temporary grounds are manually removed. • An automatic application is launched and applies the voltage to a given circuit while the others remain grounded. • The discharge is controlled by the system and current to 0 is automaticallymeasured. • Selection to the next circuit is done automatically via an internal switching board at 0 current. The circuit previously under test is grounded and the next one is open for voltage application.
Definition of electrical safety subsector Electrical safety subsector • Circuits sharing the same cryogenic environment, which can accidentally come into contact, shall be considered to belong to the same electrical safety subsector. • Circuits closer than 30 cm from circuits shall be defined as being in neighborhood “voisinage”. (dipole correctors, heater power supply, instrumentation rack and instrumentation systems). powering subsectors
ELQA activities and related risks I • Electrical • Wide geographical extension of the electrical subsectors over few km (arcs). • Live parts (current leads) are accessible. • Components connected live to a circuit may also be energized (instrumentation cabling, temperature routing, current lead heating systems…). • Most of the test are in the BT regime. • Two tests in the HTA regime. • HVQ: 1.9 kV dc are applied to the MB circuit. • DPC: up to 150 V dc are applied to the MB circuit. • Working environment • Sometimes delicate accessibility to equipment on top of the DFB’s VIC
ELQA activities and related risks II Where: Local dipole orbit correctors Protection degree:IP00 live! When: During ELQA DOC Risk:Extremely high Action 1: Fully automatic HVQ test Action 2: Follow the safety procedure Where: DFB instrumentation rack Protection degree: <IP45 When: During ELQA TP4 Risk: low Action: Do not touch
ELQA activities and related risks III Where: DFB Current leads Protection degree:IP00 live! When: During ELQA TP4 Risk:Extremely high Action 1: Fully automatic HVQ test Action 2: Follow the safety procedure Where: IFS instrumentation box and QPS Protection degree: <IP45 When: During ELQA TP4 Risk: low Action: Do not touch
ELQA actors • The requester: Project Engineer (PE) • Responsible for: • Organize and plan ELQA activities. • Request of intervention to the EIC. • The Operation Engineer (OE) is the “charge de travaux” hab. B2 • Responsible for: • Definition of the concerned electrical safety subsectors. • Determine the list of power converters and heater power supplies to be consigned and switched off (condamné) and transmit it to the Electrical Circuits Coordinator ECC for execution. • Check the correct execution done by AB/PO of the consignation step #1. Collect yellow papers. • Verify the safety measures in place for the execution of the intervention. • Ensure his own safety and the safety of the intervention team. • Inform the Electrical Circuits Coordinator ECC of the intervention completion • The Intervention Team (IT) i.e. “executant electricien” hab. B1 • in charge of: • The execution of the work / measurements.
Execution of an intervention • Example on how I see it working (not fully in place yet)
What else has to be considered • ELQA on an electrical safety subsector requires • Task file including the nature of the test (who, when, where, how) transmitted to LHC health & safety inspection team. • Global access restrictions under the responsibility of TS/HDO. • No co-activities allowed during the HVQ qualification test. • For the ELQA-DOC tests: the ELQA team in charge of the qualification takes care of all preparatory work and installation of local restrictions. • During the HVQ measurements, where voltages up to 1.9 kV are applied to the circuit, a member of the ELQA team will be placed in the energized and potentially accessible areas.
References • Safety policy at CERN (SAPOCO/42), • Electrical code C1, • UTE C 18-530, “Carnet de prescriptions de sécurité électrique destine au personnel habilité” • LHC-S-ES-0022.01 “Electrical safety rules for the superconducting circuits in the LHC” EDMS 873256 (engineering check) • Definition of the safety sub sectors: http://hcc.web.cern.ch/hcc/safety_subsec.php • LHC-DE-TP-0007.01 “ELQA Qualification of the superconducting circuits during hardware commissioning” EDMS 873256 (engineering check)