Electrical infrastructure

An estimation of the electrical power requirements for the different components of the SPL facility is presented in Table 5.9. The final power requirements will depend on the performance of the normal-conducting and supernormal-conducting RF cavities and the pulse structure used for operation.

Table 5.9: Electrical power requirements (MW) of the SPL (r.m.s. values)

Load 4 MW neutrino 5 MW EURISOL

baseline baseline

RF system^| 20:2 24:4

Cryogenics 3:6 4:4

Cooling and ventilation 4 4

Other 1 1

General services (surface C tunnel), racks, computers, controls 3 3

Total 32 37

|Including 30% margin to compensate for Lorentz-force detuning in the SC cavities.

The current study is based on the power requirements for the SPL EURISOL baseline (right col-umn). Owing to the high costs of the 4 km of 66 kV cable and power transformers, the link between

5.4 ELECTRICAL INFRASTRUCTURE

Prévessin and Meyrin already takes into consideration possible future upgrades of the SPL in order to avoid replacement of these very costly components.

So far, we assume that all major electrical loads (RF, cryogenics and CV) are stable, non-pulsating loads and that the RF pulsing is absorbed in the power supplies. However, because of the high contents of rectifier load, a Static Var Compensator (SVC) will most likely be required to obtain a satisfactory mains quality with respect to harmonic distortion and voltage stabilization. At the same time, the reactive power will be compensated such that MW and MVA are almost equal.

The overall electrical consumption will be around 40 MW. For comparison, the Meyrin electrical network with the PS and Booster in operation consumes about 25 MW during the full-load period in summer. The SPL EURISOL baseline will have almost twice the power consumption of the entire Meyrin network, and corresponds to about 30% of total LHC consumption. Owing to its large power demand, the SPL cannot be integrated into the existing electrical infrastructure of Meyrin; a new power in-feed from Prévessin and a large new 66/18 kV substation in Meyrin will be necessary (Fig. 5.9). Standard solutions developed for LEP/LHC will be applied to a large extent.

Fig. 5.9: Layout of CERN’s standard 66/18 kV substation

The total power available from the Prévessin 66 kV system is 220 MVA: two transformers, each with 110 MVA. The total existing requirements will be around 180 MVA, including the LHC require-ments estimated to be around 125–130 MVA. Adding the power requirerequire-ments for the SPL to the existing 66 kV station would bring CERN’s entire 66 kV system, including LHC, too close to 100% of its thermal limits or even overload the system. Any future upgrade of the SPL or any other additional high-power user could certainly not be covered with the existing 400 kV installation. Clearly, a new in-feed from 400 kV will be needed right from the beginning.

This will require a new 400 kV bay in CERN’s major 400 kV substation, including a new 400/66 kV transformer in Prévessin. From the 66 kV side of the transformer there will be a 66 kV cable from Prévessin to Meyrin, terminating in Meyrin with a 66/18 kV transformer and a major 18 kV substation.

Depending on the final power requirements of SPL upgrades or other users on the Meyrin site, the possi-bility of future extension with a second 66 kV cable and a second 66/18 kV transformer will be reserved.

From the 18 kV substation, there will be 18 kV cables to the 18/0.4 kV individual distribution trans-formers and to the 18/3.3 kV transtrans-formers for cryogenics, as well as to large RF power converters being supplied directly from the 18 kV level (see Fig.5.10).

new transformer 66/18 kV 70...110 MVA 66 kV cable link 4 km 400/66 kV 110...160 MVA new transformer

66 kV

provision for SPL upgrades

18 kV 18 kV

RF Cryo 3.3 kV Gen. Serv. 0.4 kV

link to Meyrin 30 MVA SVC

400 kV EDF

Fig. 5.10: Proposed electrical distribution system for the SPL

Based on previous experience with repeated cable trench digging between Meyrin and Prévessin, it is strongly proposed to install a cable duct or gallery between these two major CERN sites. Previous experience has shown that such a cable duct would be amortized within five to seven years, since addi-tional cabling needs (including optical fibres) arise on average every three years. This would give the possibility of a second 66 kV link and of a new crucial 18 kV cable MP6 between Prévessin and Meyrin.

Depending on the final power requirements and their geographical distribution, there might be the need for an underground cavern for an electrical substation.

The new electrical system is proposed as follows:

400 kV system (Prévessin): An additional 400 kV bay, including a 400/66 kV transformer and circuit breaker. Displacement or modification (into two levels) of the existing 400 kV incoming overhead line will be required in order to gain the space for the transformer and circuit breaker.

66 kV system: The 400/66 kV transformer will supply a new 66 kV station with two outgoing feeders. One feeder is needed for the SPL EURISOL baseline, and there should be provision for a second one for possible SPL upgrades or future additional users. At the Meyrin end of the 66 kV cable, there will be a 66/18 kV transformer rated 70 MVA, feeding a new major 18 kV substation. It is proposed to install the 66/18 kV station in the close vicinity of the SPL to minimize cabling and electrical losses.

18 kV system (Meyrin): The 18 kV system will be the backbone of the SPL power distribution.

The 18 kV substation will be directly behind the main 66/18 kV transformer, as the connection needs to transmit very high currents. As a rough estimation, a large substation with about 30 cubicles will be required to transmit the power of 40 MW. In addition, a 30 MVA bidirectional connection to the Meyrin 18 kV network (Station SW or ME9) is proposed in order to have a backup supply in both directions, for critical infrastructures. As for the LHC, the 18 kV station will be divided into two individual sections for Machine and General Services.